PARTIALLY PLATED PLASTIC PRODUCT

Info

Publication number: 20170306518
Type: Application
Filed: Apr 17, 2017
Publication Date: Oct 26, 2017
Inventors: Moriyuki HASHIMOTO (Kiyosu-shi), Kimihiro IIMURA (Kiyosu-shi)
Application Number: 15/488,591

Abstract

A partially plated plastic product includes a first base member and a second base member that are made of different plastic materials. The first base member includes a first corner portion having a curved wall surface. The second base member includes a second corner portion. The first and second corner portions are located on a front side of the product. The first and second base members are adjacent to each other at least at the first corner portion and the second corner portion. Only one of the first and second base members includes a metal coating film formed on a region of an outer surface of the base member with which the other base member is not in contact. The second corner portion includes a groove forming portion. The groove forming portion forms a groove between itself and at least the curved wall surface of the first corner portion.

Description

Description

BACKGROUND OF THE INVENTION

The present invention relates to a partially plated plastic product that includes a first base member and a second base member made of different plastic materials. A metal coating film is formed on a region of the outer surface of one of the base members that is not in contact with the other.

The first base member and the second base member in this type of partially plated plastic product are molded in order by two-color molding. Thereafter, for example, a metal coating film is formed on a region of the outer surface of the first base member that is not in contact with the second base member, so that a partially plated plastic product is produced (see, for example, Japanese Laid-Open Patent Publication Nos. 2005-100964 and 2010-33942).

One form of such a partially plated plastic product is shown in FIG. 9. This partially plated plastic product 70 includes a first base member 71 and a second base member 73, which are adjacent to each other at least at a first corner portion 72 on the front side of the first base member 71 and a second corner portion 74 on the front side of the second base member 73. The intended shapes of the first corner portion 72 and the second corner portion 74 are angular shapes as shown in FIG. 9. A metal coating film 75 is formed by plating in a region of the outer surface of the first base member 71 with which the second base member 73 is not in contact. The metal coating film 75 is not formed on the outer surface of the second base member 73.

In the conventional partially plated plastic product 70, it is difficult to mold the angular shape of the first corner portion 72 using a mold. Specifically, the first corner portion 72 is molded with the molding recess of the mold, and it is difficult to form the inner corner portion of the molding recess into an angular shape by NC machining, electric discharge machining, polishing process or the like. Therefore, as shown in FIGS. 10A and 10B, a relatively large convex curved wall surface 76 is formed in the first corner portion 72.

Therefore, during the molding of the second base member 73 performed after the molding of the first base member 71, a gap may be generated between the second corner portion 74 and the curved wall surface 76 of the first corner portion 72 due to short shot. The short shot refers to a phenomenon in which molten plastic does not reach the deepest parts of the molding space between the curved wall surface 76 and the mold due to the flowability of molten plastic, the gas retained in the molding space for molding the second corner portion 74, and the like.

The first base member 71 and the second base member 73, which are obtained in the above described manner, constitute an intermediate product, which is then subjected to a plating process. During the plating process, the plating solution enters the above-described gap. When the intermediate product is taken out from a first plating tank, the plating solution that has entered the gap remains in the gap due to the surface tension. The intermediate product is then brought into a second plating tank. Thus, in the second plating tank, the plating solution remaining in the gap can flow out so that the metal coating film 75 may not be properly formed on the first base member 71, particularly on the first corner portion 72, and the base may be exposed.

The position of the outer edge of the second corner portion 74 varies due to short shots. This varies a parting line 78, which is the outer edge of the metal coating film 75 on the first corner portion 72.

As a result, the appearance of the boundary between the first corner portion 72 and the second corner portion 74 deteriorates.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide a partially plated plastic product that improves the appearance of the boundary between a first corner portion and a second corner portion.

To achieve the foregoing objective and in accordance with one aspect of the present invention, a partially plated plastic product is provided that includes a first base member and a second base member that are made of different plastic materials. The first base member includes a first corner portion. The second base member includes a second corner portion. The first corner portion and the second corner portion are located on a front side of the partially plated plastic product. The first base member and the second base member are adjacent to each other at least at the first corner portion and the second corner portion. The first corner portion includes a convex curved wall surface. Only one of the first base member and the second base member includes a metal coating film formed on a region of an outer surface of the base member with which the other base member is not in contact. The second corner portion includes a groove forming portion that forms a groove between itself and at least the curved wall surface of the first corner portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a partial cross-sectional view of a partially plated plastic product according to a first embodiment.

FIG. 1B is an enlarged partial cross-sectional view showing a part of FIG. 1A.

FIGS. 2A to 2C are partial cross-sectional views illustrating processes of molding a first base member and a second base member using a mold in the first embodiment.

FIG. 3 is a schematic explanatory diagram showing an electroplating process in a manufacturing process of a partially plated plastic product in the first embodiment.

FIG. 4A is a partial cross-sectional view of a partially plated plastic product according to a second embodiment.

FIG. 4B is an enlarged partial cross-sectional view showing a part of FIG. 4A.

FIGS. 5A to 5C are partial-cross-sectional views of partially plated plastic products according to modifications of the first embodiment.

FIGS. 6A to 6C are partial-cross-sectional views of partially plated plastic products according to modifications of the first embodiment.

FIGS. 7A and 7B are partial-cross-sectional views of partially plated plastic products according to modifications of the first embodiment.

FIG. 8A is a partial-cross-sectional view of a partially plated plastic product according to a modification of the first embodiment.

FIG. 8B is an enlarged partial cross-sectional view showing a part of FIG. 8A.

FIG. 9 is an explanatory diagram of a conventional partially plated plastic product, in which a first corner portion and a second corner portion are formed into intended shapes.

FIG. 10A is a partial cross-sectional view of the conventional partially plated plastic product.

FIG. 10B is an enlarged partial cross-sectional view showing a part of FIG. 10A.

FIG. 11 is a partial cross-sectional view of another conventional partially plated plastic product.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A partially plated plastic product according to a first embodiment will now be described with reference to FIGS. 1 to 3. Partially plated plastic products are employed as vehicle exterior parts such as grilles, fog light covers, and the like.

FIG. 1A shows a cross-sectional structure of part of the partially plated plastic product 10. FIG. 1B is an enlarged view of part of FIG. 1A. In FIGS. 1A and 1B, the upper side corresponds to the front side, or a design surface side, of the partially plated plastic product 10, and the lower side corresponds the back side. The front-back direction coincides with the parting direction of mold halves 35, 36, which are used to mold an intermediate product 48 constituted by a first base member 11 and a second base member 21 discussed below.

The frame of the partially plated plastic product 10 is constituted by the first base member 11 and the second base member 21, which are made of different plastic materials.

The first base member 11 is made of acrylonitrile-butadiene-styrene copolymer (ABS). The first base member 11 has a recess 12 that is dented from the front side surface toward the back side. The first base member 11 also has a first corner portion 14 on the front side. The first corner portion 14 is located at the periphery of the recess 12. That is, the first corner portion 14 is located on the front side of the partially plated plastic product 10. Part of the front side surface of the first base member 11 around the recess 12 and adjacent to the first corner portion 14 is constituted by a flat general wall surface 13. The first corner portion 14 includes a convex curved wall surface 15 and has a sectoral cross section with a central angle α of 85°. The convex curved wall surface 15 is curved with a radius R of about 0.3 mm.

The first corner portion 14 has an upright wall surface 16 that connects the curved wall surface 15 and a bottom surface 12a of the recess 12. The upright wall surface 16 is constituted by a flat surface extending from the curved wall surface 15 in a direction intersecting substantially perpendicularly to the general wall surface 13.

The second base member 21 is made of a colored plastic material containing polycarbonate (PC) as a main component. The colored plastic material refers to a material obtained by coloring plastic itself by mixing a colorant such as a pigment into a plastic material (PC) or by mixing a glittering material together with a colorant into a plastic material (PC).

Part of the second base member 21 is formed to fill the recess 12 of the first base member 11. Part of the second base member 21 that is adjacent to the first corner portion 14 of the first base member 11 constitutes a second corner portion 22. The second corner portion 22 is located on the front side of the second base member 21. That is, the second corner portion 22 is located on the front side of the partially plated plastic product 10. Part of the front side surface of the second base member 21 that is adjacent to the second corner portion 22 is constituted by a general wall surface 23. The general wall surface 23 is flat and is located on the same plane as the general wall surface 13 of the first base member 11.

The second corner portion 22 has a groove forming portion 25. A groove 24 is formed between the groove forming portion 25 and at least the curved wall surface 15 of the first corner portion 14. The groove forming portion 25 has a flat inclined wall surface 26. The inclined wall surface 26 is inclined with respect to the upright wall surface 16 such that, toward the front side, the inclined wall surface 26 is inclined away from the first corner portion 14. When the depth of the groove 24 is denoted by D, the inclined wall surface 26 is in contact with the upright wall surface 16 at a position separated from the general wall surface 23 toward the back side by a depth D of 1.0 mm or more. The portion where the inclined wall surface 26 is in contact with the upright wall surface 16 is a portion closer to the front side than the bottom surface 12a of the recess 12.

The angle θ formed by the inclined wall surface 26 with respect to the upright wall surface 16 is preferably 60° or more. The groove 24 is formed by a molding protrusion 42 (see FIG. 2B) provided on a second fixed mold half 41, which will be discussed below, and the preferred angle is a condition required to ensure the strength of the molding protrusion 42. In the first embodiment, the angle θ is set to 60°.

The width W of the groove 24, which is formed between the first corner portion 14 and the groove forming portion 25, is minimized at the deepest part of the groove 24. More specifically, the groove 24 has a shape (a substantially V-shaped cross section) in which the groove width W decreases toward the deepest part.

A metal coating film 31 is formed by plating in a region of the outer surface of the first base member 11 with which the second base member 21 is not in contact. Part of the metal coating film 31 is formed on the general wall surface 13. Another part of the metal coating film 31 is formed on the first corner portion 14. In the groove 24, the metal coating film 31 is formed on the curved wall surface 15 and part of the upright wall surface 16 that faces the groove 24. In contrast, the metal coating film 31 is not formed on the outer surface of the second base member 21. The portion of the inclined wall surface 26 that is in contact with the upright wall surface 16 is merely in contact with an end portion 33 of the metal coating film 31. That is, the end portion 33 is not formed in the part of the inclined wall surface 26 that is in contact with the upright wall surface 16.

Operation and advantages of the first embodiment, which is configured as described above, will now be described, together with a method for manufacturing the partially plated plastic product 10.

First, the first base member 11 and the second base member 21 are molded by two-color molding process. In the two-color molding, a mold 35 for molding the first base member 11 shown in FIG. 2A and a mold 36 for molding the second base member 21 shown in FIG. 2B are used.

The molds 35, 36 have two kinds of fixed mold halves and a common movable mold half 45, which approaches and separates from the fixed mold halves. The two types of fixed mold halves are a first fixed mold half 37 and a second fixed mold half 41. As shown in FIG. 2A, the first fixed mold half 37 has a molding recess 38 for molding the first corner portion 14, which has the curved wall surface 15 and the upright wall surface 16. The inner corner portion of the molding recess 38 has a curved wall surface 39 that is curved with a radius of approximately 0.3 mm. The curved wall surface 39 is formed by machining the first fixed mold half 37 by NC machining, electric discharge machining, polishing process or the like. That is, depending on these processing methods, it is difficult to form the inner corner portion of the molding recess 38 into an angular shape. The curved wall surface 39, which is curved with a radius of approximately 0.3 mm at the minimum, is formed in the inner corner portion of the molding recess 38.

As shown in FIG. 2A, the mold 35 for molding the first base member 11 uses the first fixed mold half 37 as a fixed mold half. When the mold 35 is clamped, a molding space 46 (cavity) for molding the first base member 11 is formed between the first fixed mold half 37 and the movable mold half 45. Part of the molding space 46 is constituted by the molding recess 38. Molten plastic is supplied from the gate (not shown) provided in the mold 35 to the molding space 46. By curing the molten plastic filling the molding space 46, the first base member 11 is molded, which has the curved wall surface 15 and the upright wall surface 16 at the first corner portion 14.

Next, when the mold 35 is opened, the movable mold half 45 is separated from the first fixed mold half 37. At this time, the first base member 11 is separated from the first fixed mold half 37 together with the movable mold half 45, while adhering to the movable mold half 45.

As shown in FIG. 2B, the mold 36 for molding the second base member 21 uses the second fixed mold half 41 as a fixed mold half. The second fixed mold half 41 has the molding protrusion 42 for molding the second corner portion 22 on the second base member 21. The molding protrusion 42 has an inverse shape of that of the groove 24. That is, the molding protrusion 42 has a shape in which its thickness is the maximum at its root and decreases toward its tip. Such a shape is easier to fabricate than that in the case where the inner corner portion of the molding recess 38 is machined into an angular shape.

As shown in FIG. 2B, the movable mold half 45 with the adhered first base member 11 is brought close to the second fixed mold half 41 to clamp the mold 36. The clamping operation forms the molding space 47 for molding the second base member 21, which has the second corner portion 22, between the first base member 11 and the second fixed mold half 41. Part of the molding space 47 is constituted by the molding protrusion 42.

Molten plastic is supplied from the gate (not shown) provided in the mold 36 to the molding space 47. By curing the molten plastic filling the molding space 47, the second base member 21, which has the groove forming portion 25 at the second corner portion 22, is molded as shown in FIG. 2C. The second corner portion 22 is formed between the molding protrusion 42 of the second fixed mold half 41 and the bottom surface 12a of the recess 12 in the first base member 11.

When the second corner portion 22 is formed, the groove 24 is formed, in which the groove width W decreases toward the deepest end, between the groove forming portion 25 and the first corner portion 14.

The inclined wall surface 26 is separated from the curved wall surface 15. Thus, formation of the second corner portion 22 is unlikely to be affected by the curved wall surface 15. That is, the molding space 47 for molding the second corner portion 22 has no space that gradually narrows and hinders flow of molten plastic, like the space between the conventional curved wall surface 76 and the die half.

Thus, when forming the second corner portion 22 of the first embodiment, short shots are unlikely to occur, which may occur due to the influence of the curved wall surface 76 when forming the second corner portion 74 in contact with the curved wall surface 76 in the conventional configuration. Further, in the conventional partially plated plastic product 70, when a short shot occurs, the end of the second corner portion 74 is not neatly rounded, and projections such as burrs may be formed. In contrast, since the first embodiment restrains the occurrence of short shots, such projections are unlikely to to be formed.

Accordingly, the second corner portion 22 having a stable shape as shown in FIG. 1B is formed. The part of the inclined wall surface 26 that contacts the upright wall surface 16 is defined as an outer edge 22a of the second corner portion 22. The position of the outer edge 22a varies less than that in the conventional configuration. The outer edge 22a corresponds to the parting portion between the first corner portion 14 and the second corner portion 22. In this manner, the intermediate product 48 (see FIG. 2C) is obtained, in which the first base member 11 and the second base member 21 are integrated.

The melting point of PC used as the material for forming the second base member 21 is higher than the melting point of ABS used as the material for forming the first base member 11. The first base member 11 is formed prior to the formation of the second base member 21. Thus, when PC in a molten state is supplied to the molding space 47, the PC in a molten state having a temperature higher than the melting point of the first base member 11 comes into contact with the first base member 11. The heat of the molten PC is transferred to the first base member 11 and melts the interface between the first base member 11 and the second base member 21. The second base member 21 is formed to closely contact the first base member 11.

Subsequently, a process of partially plating the intermediate product 48 is performed.

First, the intermediate product 48 is attached to a jig 50 shown in FIG. 3. The jig 50 includes a jig main body 51, a metal clip (not shown), and a hook portion 53. The metal clip is provided on the jig main body 51 and holds an electric contact portion 49 provided on the intermediate product 48. The hook portion 53 hooks the jig main body 51 onto a conveyor 52. The conveyor 52 moves the jig 50, to which the intermediate product 48 is attached, in the vertical direction and the horizontal direction. The conveyor 52 moves the jig 50 to a position outside the plating tank 54 where the conductivity imparting step is performed. Thereafter, the jig 50 is moved to various plating tanks 54 by the conveyor 52, and electroplating processes are performed.

In this process, the following surface treatments are performed on the jig 50 and the intermediate product 48. First, foreign matter such as dust, oil, and the like adhering to the outer surface of the intermediate product 48 is removed by conditioning the surface of the intermediate product 48. Next, the intermediate product 48 is chemically roughened by etching the intermediate product 48 using an etching solution. Then, the outer surface of the intermediate product 48 is neutralized with acid to reduce and remove hexavalent chromium, which is one type of etching component. Subsequently, a catalyst that has a strong adsorbability and a reducing power (Pd—Sn compound) is applied to and adsorbed by the roughened outer surface of the intermediate product 48. Then, an accelerator is applied to the intermediate product 48 to remove Sn from the outer surface of the intermediate product 48, thereby activating Pd. Next, the intermediate product 48 is immersed in an electroless plating tank, and electroless plating is performed on the intermediate product 48, thereby forming an electroless plated layer. Through the conductivity imparting process, conductivity is imparted to the outer surface of the intermediate product 48.

In this process, as shown in FIG. 3, the intermediate product 48 is immersed in the various plating tanks 54 together with the jig 50. The various plating tanks 54 each store corresponding plating solution 55. Each of the various plating tanks 54 includes an anode electrode 56. In the electroplating process, an anode voltage is applied to the anode electrode 56. Further, a cathode voltage is applied to the intermediate product 48 through the electric contact portion 49 held by the clip. Since the conductive electroless plated layer described above is formed on the outer surface of the intermediate product 48, the outer surface is negatively charged.

In various electroplating processes, acid activation, strike plating, copper plating, semi-gloss nickel plating, gloss nickel plating, dispersion strike nickel plating, and chrome plating are performed in order.

Thus, when each of the electroplating processes is performed and cathode voltage is applied to the intermediate product 48, the region of the outer surface of the first base member 11 with which the second base member 21 is not in contact is negatively charged. Therefore, positive charges of the metal component dissolved in the plating solution 55 are gathered around the first base member 11 to form the metal coating film 31.

In the groove 24, the metal coating film 31 is formed on the curved wall surface 15 and part of the upright wall surface 16 that faces the groove 24 as shown in FIG. 1B. The metal coating film 31 is not formed on the groove forming portion 25. When the outer edge of the metal coating film 31 is defined as a parting line 32, the parting line 32 is located in the vicinity of part at which the inclined wall surface 26 and the upright wall surface 16 are in contact with each other (the outer edge 22a), that is, a position separated from the outer edge 22a by the distance substantially corresponding to the thickness of the metal coating film 31.

The volume of the groove 24, which is formed between the groove forming portion 25 and the first corner portion 14 as described above, is larger than the volume of the gap formed between the first corner portion 72 and the second corner portion 74 in the conventional partially plated plastic product 70, in which the groove 24 is not formed.

In particular, in the first embodiment, the inclined wall surface 26, which is inclined with respect to the upright wall surface 16, is in contact with the upright wall surface 16. Therefore, the groove 24 is deeper than in the case where the inclined wall surface 26 is in contact with the curved wall surface 15, so that the groove 24 has a large volume.

Therefore, even if the plating solution 55 enters the groove 24 when the plating process is performed on the intermediate product 48, the plating solution 55 is easily drained when the intermediate product 48 is taken out from the plating tank 54.

Further, as described above, the width W of the groove 24 decreases toward the deepest part of the groove 24, and is the smallest at the deepest part of the groove 24. Therefore, when the intermediate product 48 is taken out from the plating tank 54, the plating solution 55 that has entered the groove 24 during the plating process is drained from the part where the groove width W is largest in the groove 24. This allows for efficient drainage of the plating solution 55.

As a result, unlike the conventional partially plated plastic product, the intermediate product with the plating solution 55 remaining in the groove 24 is not likely to be brought into the next plating tank 54, so that the remaining plating solution 55 affects the deposition of the metal coating film 31 on the outer surface of the first base member 11. Therefore, the metal coating film 31 is properly formed on the first base member 11, particularly the first corner portion 14 without exposing the base.

In the groove 24, the curved wall surface 15 and part of the upright wall surface 16, on which the metal coating film 31 is formed, are separated from the second corner portion 22 except for the portion of the upright wall surface 16 that is in contact with the inclined wall surface 26. Thus, the formation of the metal coating film 31 is unlikely to be affected by the second corner portion 22. The metal coating film 31 is formed on the curved wall surface 15 and the upright wall surface 16 in a stable state. In other words, the metal coating film 31 is formed with high adhesion to the curved wall surface 15 and the upright wall surface 16.

In addition, as described above, since the variation in the shape of the second corner portion 22 is small, the variation in the position of the outer edge 22a of the second corner portion 22 is smaller than that in the conventional configuration. This reduces the variation of the outer edge (parting line 32) of the metal coating film 31 formed at the boundary with the inclined wall surface 26 on the first corner portion 14.

In this manner, the base of the first base member 11 is not exposed, and the metal coating film 31 having small variations in the parting line 32 is formed on the outer surface of the first base member 11.

Thereafter, sequential execution of a drying process, removal of the jig 50, and inspection produces an objective partially plated plastic product 10, which has a metal coating film 31 on part of the outer surface.

In the partially plated plastic product 10, the variation of the parting line 32 of the metal coating film 31 is small as described above. As a result, the appearance of the boundary between the first corner portion 14 and the second corner portion 22 is improved as compared to that in the conventional partially plating plastic product 70, in which a gap exists between the first corner portion 72 and the second corner portion 74.

In particular, the upright wall surface 16 is arranged so as to be substantially orthogonal to the general wall surface 13 of the first base member 11. The parting line 32 is located in the vicinity of the upright wall surface 16. Therefore, even if the position of the parting line 32 varies somewhat in the front-back direction along the upright wall surface 16, such a variation has a limited influence on the appearance.

Also, from the front side of the partially plated plastic product 10, the metal coating film 31 formed on the general wall surface 13 of the first base member 11 and the general wall surface 23 of the second base member 21 appear to be positioned on substantially the same plane. Since it appears that no or only a small step exists between the metal coating film 31 and the general wall surface 23, the appearance of the partially plated plastic product 10 is improved.

Furthermore, as described above, in the conventional partially plated plastic product 70, when a short shot occurs, projections such as burrs may occur at the second corner portion 74. If a metal coating film is formed on such projections by plating process, light reflected by the metal coating film on the projections may flicker. However, in the first embodiment, since projections are unlikely to be formed as described above, flickering is unlikely to occur due to the formation of the metal coating film 31 on projections.

In addition to the above-mentioned advantages, the first embodiment is superior to the conventional partially plated plastic product 70 in the following points.

FIG. 11 shows a conventional partially plated plastic product 70 employed as a vehicle exterior part. This partially plated plastic product 70 includes a first base member 71 and a second base member 73, which are adjacent to each other at least at a first corner portion 72 on the front side of the first base member 71 and a second corner portion 74 on the front side of the second base member 73. The metal coating film 75 is formed on the outer surface of the first base member 71, but is not formed on the second base member 73. The metal coating film 75 includes a main body portion 81 and an end portion 82. Part of the end portion 82 protrudes from the first base member 71 and is positioned on the second base member 73. However, part of the end portion 82 located on the second base member 73 is merely in contact with the second corner portion 74.

Since vehicle exterior parts are used under severe environments such as weather conditions compared to vehicle interior parts, the metal coating film 75 is formed to have a greater thickness than the metal film on partially plated plastic products employed as the vehicle interior parts.

Electric charge in the plating solution tends to concentrate more on the end portion 82 of the metal coating film 75 than on the main body portion 81. Therefore, the amount of plating deposited on the end portion 82 is greater than the amount of plating deposited on the main body portion 81. Therefore, the film thickness of the end portion 82 is greater than the film thickness of the main body portion 81, and the end portion 82 has a convex shape bulging further toward the front side than the main body portion 81. This tendency is common not only to the partially plated plastic product 70 but also to plated plastic products in general.

In a case where the partially plated plastic product 70 is employed as a vehicle exterior part in which the film thickness of the main body portion 81 is originally great, the difference between the film thickness of the end portion 82 and the film thickness of the main body portion 81 is larger than in a case where the partially plated plastic product 70 is employed as a vehicle interior part. Therefore, when the partially plated plastic product 70 is employed as a vehicle exterior part, the end portion 82 has a convex shape bulging further toward the front side than the main body portion 81, which degrades the appearance at the boundary between the first corner portion 72 and the second corner portion 74.

Furthermore, when the film thickness of the end portion 82 having a convex shape is excessive, a phenomenon occurs in which plating is locally excessively deposited in the end portion 82 to form protrusions 83. This further degrades the appearance of the partially plated plastic product 70.

The end portion 82 is in contact with the second corner portion 74 of the second base member 73 but is not bonded thereto. The metal coating film 75 includes a copper coating film. Therefore, when liquid that corrodes the copper coating film in the metal coating film 75 enters through the gap between the end portion 82 and the second corner portion 74, the copper coating may be corroded. Particularly, when a finger or the like touches the end portion 82 or an impact is applied to the end portion 82, the end portion 82 peels off and the gap between the end portion 82 and the second corner portion 74 expands. The liquid easily enters the expanded gap, promoting corrosion of the copper coating film.

In contrast, in the first embodiment shown in FIGS. 1A and 1B, part of the metal coating film 31 is formed on the curved wall surface 15 and the part of the upright wall surface 16 that faces the groove 24. The end portion 33 of the metal coating film 31 is formed on the upright wall surface 16. As shown in FIG. 1A, the curved wall surface 15 and the upright wall surface 16 are located at a position further away from the anode electrode 56 toward the back side than the general wall surface 13.

Thus, positive charges of the metal component dissolved in the plating solution 55 are less likely to gather to the curved wall surface 15 and the upright wall surface 16 than to the general wall surface 13. Therefore, the amount of plating deposited on each of the curved wall surface 15 and the upright wall surface 16 is smaller than the amount of plating deposited on the general wall surface 13.

Further, the plating solution 55 around the first corner portion 14 is more likely to reach the general wall surface 13 than reaching the curved wall surface 15 and the upright wall surface 16. The plating is first deposited on the general wall surface 13, and accordingly the amount of plating deposited on the curved wall surface 15 and the upright wall surface 16 thereafter is small.

Accordingly, it is possible to prevent the end portion 33 from having an excessive film thickness on the curved wall surface 15 and the upright wall surface 16. Thus, the end portion 33 does not have a convex shape. Furthermore, the occurrence of a phenomenon in which protrusions are formed in the end portion 33 is suppressed. As a result, the appearance of the boundary between the first corner portion 14 and the second corner portion 22 is further improved.

Further, the end portion 33 is in the groove 24 and is located at the deepest part of the groove 24. Thus, it is unlikely that a finger or the like touches the end portion 33 or an impact is applied to the end portion 33. The end face of the end portion 33 is not attached to the inclined wall surface 26, but the gap between the end portion 33 and the inclined wall surface 26 is not easily expanded. Therefore, it is difficult for liquid that corrodes the copper film in the metal coating film 31 to enter the gap, so that corrosion of the copper coating film is suppressed. As a result, it is possible to improve the peeling resistance and rust prevention of the metal coating film 31.

In the first embodiment, the groove 24 is preferably formed such that the angle θ formed by the inclined wall surface 26 with respect to the upright wall surface 16 has a value in the range from 60° to 120°, the groove width W has a value in the range from 0.7 mm to 5.0 mm, and the depth D has a value in the range from 0.2 mm to 1.5 mm. When the groove 24 meets these conditions, it is possible to satisfactorily improve the appearance, peeling resistance, and rust prevention of the partially plated plastic product.

Second Embodiment

Next, a partially plated plastic product according to a second embodiment will be described with reference to FIGS. 4A and 4B.

The second embodiment is similar to the first embodiment in that a first corner portion 14 has a curved wall surface 15 and an upright wall surface 16. As in the first embodiment, the upright wall surface 16 is constituted by a flat surface extending from the curved wall surface 15 in a direction intersecting substantially perpendicularly with a general wall surface 13 of a first base member 11.

In the second embodiment, an inclined wall surface 26 at a second corner portion 22 is in contact with the curved wall surface 15 instead of the upright wall surface 16. A region between the inclined wall surface 26 and the curved wall surface 15 constitutes a groove 24.

In the second embodiment, the first corner portion 14 has a sectoral cross section with a central angle α of 85°. The inclined wall surface 26 is in contact with a middle point M of a circular arc A in this cross section. The inclined wall surface 26 is in contact with the curved wall surface 15 at a position separated from the general wall surface 23 of the second base member 21 toward the back side by a depth D. The depth D in the second embodiment is smaller than the depth D in the first embodiment and smaller than the radius R of the curved wall surface 15.

If the tangent line passing through the middle point M of the circular arc A is defined as a tangential line TL, the angle θ formed by the inclined wall surface 26 with respect to the tangent line TL is preferably 60° or greater. As in the first embodiment, the groove 24 is formed by the molding protrusion 42 (see FIG. 2B) provided on the second fixed mold half 41, and the preferred angle is a condition required to ensure the strength of the molding protrusion 42. In the second embodiment, the angle θ is also set to 60°.

The groove 24 is filled with part of the metal coating film 31. In this respect, the second embodiment differs from the first embodiment, in which the metal coating film 31 is formed only on the curved wall surface 15 and part of the upright wall surface 16 in the groove 24.

In the second embodiment, the metal coating film 31 is formed by laminating three types of coating films, which are a copper film 61, a nickel film 62, and a chromium film 63. The copper film 61 and the nickel film 62 each have a film thickness of approximately 50 μm, whereas the chromium film 63 has a film thickness of 1 μm or less.

Other than the above described differences, the second embodiment is the same as the first embodiment. Thus, like or the same reference numerals are given to those components that are like or the same as the corresponding components described above in the first embodiment and detailed explanations are omitted.

In the second embodiment, the inclined wall surface 26 inclined with respect to the upright wall surface 16 is in contact with the curved wall surface 15. Therefore, the groove 24 is shallower and has a smaller volume than that in the first embodiment, in which the inclined wall surface 26 is in contact with the upright wall surface 16. However, the volume of the groove 24 is larger than the volume of the gap formed between the first corner portion 72 and the second corner portion 74 in the conventional partially plated plastic product 70, in which the groove 24 is not formed.

Therefore, even if the plating solution 55 enters the groove 24 when the plating process is performed on the intermediate product 48, the plating solution 55 is easily drained when the intermediate product 48 is taken out from the plating tank 54.

Further, unlike the conventional molding space, the molding space 47 for molding the second corner portion 22 has no space that gradually narrows and hinders flow of molten plastic. Thus, short shots are unlikely to occur. Accordingly, the second corner portion 22 having a stable shape is formed. The part of the inclined wall surface 26 that contacts the curved wall surface 15 is defined as an outer edge 22a of the second corner portion 22. The position of the outer edge 22a varies less than that in the conventional configuration.

On the other hand, the groove 24, which has a small volume, is filled with part of the metal coating film 31. Therefore, the outer edge (the parting line 32) of the metal coating film 31 is unlikely to be affected by the shape of the second corner portion 22. Variation of the parting line 32 of the metal coating film 31 is less than that of the conventional partially plated plastic product, which is easily affected by the shape of the second corner portion 74.

The second embodiment thus achieves the same advantages as the first embodiment. In addition, since the groove 24 is concealed by the metal coating film 31 located in the groove 24, the second embodiment has an advantage that the groove 24 is hard to see from the front side of the partially plated plastic product 10.

In addition to the above-mentioned advantages, the second embodiment is superior to the conventional partially plated plastic product 70 in the following points.

In the second embodiment, the end portion 33 is formed on the curved wall surface 15 in the groove 24. The curved wall surface 15 is located at a position further away from the anode electrode 56 toward the back side than the general wall surface 13.

Thus, the second embodiment prevents the end portion 33 of the metal coating film 31 from having an excessive film thickness on the curved wall surface 15, so that the end portion 33 does not have a convex shape. Furthermore, the occurrence of a phenomenon in which protrusions are formed in the end portion 33 is suppressed. As a result, the appearance of the boundary between the first corner portion 14 and the second corner portion 22 is improved as in the first embodiment.

In the second embodiment, parts of end portions of the chromium film 63 and the nickel film 62 are located outside the groove 24 and are in contact with the second base member 21 without being bonded thereto. Thus, when a finger or the like touches the end portion 33 of the metal coating film 31 or an impact is applied to the end portion 33, the chromium film 63 and the nickel film 62 may peel off, so that the gap between the second base member 21 and the chromium film 63 and the gap between the second base member 21 and the nickel film 62 may be enlarged. However, the end portion of the copper film 61, which tends to rust, is formed at the deepest part in the groove 24 and adjacent to the back side of the nickel film 62. Thus, even if liquid that corrodes the copper film 61 enters the gap, it is unlikely to reach the copper film 61. Therefore, the second embodiment also improves the rust prevention.

The above embodiments may be modified as follows.

In the first embodiment, the metal coating film 31 may be constituted by a coating film of a single layer or a coating film of two or more layers.

In the second embodiment, the metal coating film 31 may be constituted by a coating film of a single layer. In the second embodiment, the metal coating film 31 may be constituted by a coating film of two layers or a coating film of four or more layers.

Contrary to the first and second embodiments, the first base member 11 may be formed of PC, and the second base member 21 may be formed of ABS. In this case, the metal coating film 31 is formed on the region of the outer surface of the second base member 21 with which the first base member 11 is not in contact. Although the object on which the metal coating film 31 is formed is different, the same advantages as in the first and second embodiments are achieved.

The inclined wall surface 26 of the second base member 21 is not limited to a flat surface, but may be curved to bulge toward the front side or may be curved to be recessed toward the back side.

In the partially plated plastic product 10, the general wall surface 13 of the first base member 11 and the general wall surface 23 of the second base member 21 may be positioned on different planes.

For example, in the partially plated plastic product 10, the metal coating film 31 (the outer surface) on the general wall surface 13 of the first base member 11 and the general wall surface 23 of the second base member 21 may be positioned on the same plane. In this case, the general wall surface 13 of the first base member 11 is located at a position displaced toward the back side by the amount corresponding to the film thickness of the metal coating film 31 with respect to the general wall surface 23 of the second base member 21.

In this case, from the front side of the partially plated plastic product 10, it appears that no step exists between the metal coating film 31 on the general wall surface 13 of the first base member 11 and the general wall surface 23 of the second base member 21. This further improves the appearance of the partially plated plastic product 10.

At least one of the general wall surface 13 of the first base member 11 and the general wall surface 23 of the second base member 21 may be constituted by a nonplanar, for example, a curved surface.

The partially plated plastic product 10 in the first embodiment may be modified as long as it satisfies the following conditions.

Condition 1: The first base member 11 and the second base member 21 are formed of different plastic materials. The first base member 11 has the first corner portion 14 on the front side, and the second base member 21 has the second corner portion 22 on the front side. That is, the first corner portion 14 and the second corner portion 22 are located on the front side of the partially plated plastic product 10. The first base member 11 and the second base member 21 are adjacent to each other at least at the first corner portion 14 and the second corner portion 22. The first corner portion 14 has the convex curved wall surface 15.

Condition 2: One of the first base member 11 and the second base member 21 includes the metal coating film 31 formed on a region of the outer surface of the base member with which the other base member is not in contact. The metal coating film 31 is not formed on the outer surface of the latter base member. In other words, only one of the first base member 11 and the second base member 21 includes the metal coating film 31 formed on a region of the outer surface of the base member with which the other base member is not in contact. A portion on which “the metal coating film 31 is not formed” includes a portion that contacts the metal coating film 31 but is not bonded to the metal coating film 31.

Condition 3: The second corner portion 22 includes the groove forming portion 25. The groove forming portion 25 forms the groove 24 between itself and at least the curved wall surface 15 of the first corner portion 14.

FIGS. 5A to 5C, 6A to 6C, 7A, 7B, 8A, and 8B show examples of modifications that satisfy the above three conditions. Hereinafter, the respective modifications will be described focusing on differences from the first embodiment and other modifications. Like or the same reference numerals are given to those components that are like or the same as the corresponding components described above in the first embodiment and detailed explanations are omitted.

In the first embodiment, the groove forming portion 25 is constituted by the convex curved wall surface and the inclined wall surface 26. In the first embodiment, the curved wall surface is illustrated but not described. The groove forming portion 25 is in contact with the upright wall surface 16 on the inclined wall surface 26. The region surrounded by the groove forming portion 25, the curved wall surface 15, and the upright wall surface 16 constitutes the groove 24 having a substantially V-shaped cross-sectional shape. In the groove 24, the metal coating film 31 is formed on the curved wall surface 15 and the upright wall surface 16. The end face of the end portion 33 of the metal coating film 31 is in contact with the groove forming portion 25 on the inclined wall surface 26.

In contrast, in the modification of FIG. 5A, the groove forming portion 25 is constituted by a convex curved wall surface 27, an inclined wall surface 26, and an inner bottom surface 28. The inner bottom surface 28 is formed by a plane parallel to the general wall surfaces 13, 23. The groove forming portion 25 is in contact with the upright wall surface 16 on the inner bottom surface 28. The groove 24 is constituted by the region surrounded by the groove forming portion 25, the curved wall surface 15, and the upright wall surface 16, and has a cross-sectional shape different from that of the first embodiment. In the groove 24, the metal coating film 31 is formed on the curved wall surface 15 and part of the upright wall surface 16 that faces the groove 24. The end face of the end portion 33 of the metal coating film 31 is in contact with the groove forming portion 25 on the inner bottom surface 28.

In the modification of FIG. 5B, the inner bottom surface is provided in the first corner portion 14 instead of the second corner portion 22, and the inner bottom surface 17 is connected to the lower end of the upright wall surface 16. The groove forming portion 25 is constituted by the convex curved wall surface 27 and the inclined wall surface 26. The groove forming portion 25 is in contact with the inner bottom surface 17 on the inclined wall surface 26. The region surrounded by the groove forming portion 25, the curved wall surface 15, the upright wall surface 16, and the inner bottom surface 17 constitutes a groove 24. In the groove 24, the metal coating film 31 is formed on the curved wall surface 15, the upright wall surface 16, and the inner bottom surface 17. The end face of the end portion 33 of the metal coating film 31 is in contact with the groove forming portion 25 on the inclined wall surface 26.

In the first embodiment, the upright wall surface 16 intersects with the general wall surface 13 at an angle close to the right angle, and the inclined wall surface 26 is gently inclined with respect to the general wall surface 23.

In the modification of FIG. 5C, contrary to the first embodiment, the inclined wall surface 26 is arranged to be substantially orthogonal to the general wall surface 23, and the upright wall surface 16 is gently inclined with respect to the general wall surface 13. The angle θ formed by the inclined wall surface 26 with respect to the upright wall surface 16 is smaller than that in the first embodiment.

The upright wall surface 16 is in contact with the inclined wall surface 26, and the end face of the end portion 33 of the metal coating film 31 is in contact with the groove forming portion 25 on the inclined wall surface 26.

In the modification of FIG. 5C, the upright wall surface 16 is in contact with the inclined wall surface 26 of the groove forming portion 25. More specifically, the upright wall surface 16 is in contact with part of the inclined wall surface 26 that is away from the curved wall surface 27. In the modification of FIG. 6A, the upright wall surface 16 is in contact with the groove forming portion 25 at the boundary between the inclined wall surface 26 and the curved wall surface 27. Accordingly, the depth D of the groove 24 is shallower than that of the modification of FIG. 5C.

Also, the end face of the end portion 33 of the metal coating film 31 is in contact with the groove forming portion 25 at the boundary between the inclined wall surface 26 and the curved wall surface 27.

In the modification of FIG. 6B, the groove forming portion 25 is constituted by part of the curved wall surface 27. The curved wall surface 15 is in contact with the groove forming portion 25 on the curved wall surface 27.

Accordingly, the depth D of the groove 24 is even shallower than that of the modification of FIG. 6A.

The region between the curved wall surfaces 27 and 15 constitutes the groove 24. In the groove 24, the metal coating film 31 is formed on the curved wall surface 15. The end face of the end portion 33 of the metal coating film 31 is in contact with the groove forming portion 25 on the curved wall surface 27.

The modification of FIG. 6C is similar to the modification of FIG. 5A in that the groove forming portion 25 is constituted by the curved wall surface 27, the inclined wall surface 26, and the inner bottom surface 28.

In the modification of FIG. 6C, the upright wall surface 16 is gently inclined with respect to the general wall surface 13 as compared to the modification of FIG. 5A. Further, the inclined wall surface 26 is gently inclined with respect to the general wall surface 23 as compared to the modification of FIG. 5A. The angle formed by the upright wall surface 16 with respect to the general wall surface 13 and the angle formed by the inclined wall surface 26 with respect to the general wall surface 23 are set to be the same.

The angle θ formed by the inclined wall surface 26 with respect to the upright wall surface 16 is large (90°).

The end face of the end portion 33 of the metal coating film 31 is in contact with the groove forming portion 25 on the inner bottom surface 28.

The modification of FIG. 7A is similar to the modification of FIG. 6C in that the upright wall surface 16 and the inclined wall surface 26 are gently inclined with respect to the general wall surfaces 13, 23.

In the modification of FIG. 7A, the inner bottom surface 28 of FIG. 6C is omitted, and the groove forming portion 25 is constituted by the curved wall surface 27 and the inclined wall surface 26. Thus, the end face of the end portion 33 of the metal coating film 31 is in contact with the groove forming portion 25 on the inclined wall surface 26.

In the modification of FIG. 7B, the upright wall surface 16 is further gently inclined with respect to the general wall surface 13 as compared to the modification of FIG. 7A. Further, the inclined wall surface 26 is gently inclined with respect to the general wall surface 23 as compared to the modification of FIG. 7A. Thus, the angle θ formed by the inclined wall surface 26 with respect to the upright wall surface 16 is larger (120°) than that in the modification of FIG. 7A.

The modifications shown in FIG. 5A to 7B achieve the same actions and advantages as those of the first embodiment.

Thus, the variation in the position of the outer edge 22a of the second corner portion 22 is reduced as compared to that in the conventional configuration. It is possible to form the metal coating film 31 with small variations of the parting line 32 on the outer surface of the first base member 11 without exposing the base, and the appearance of the boundary between the first corner portion 14 and the second corner portion 22 is improved.

In addition, it is possible to suppress the occurrence of a phenomenon that the end portion 33 of the metal coating film 31 has a convex shape or protrusions are formed on the end portion 33, so that the appearance of the boundary between the first corner portion 14 and the second corner portion 22 is improved. In addition, it is possible to improve both the peeling resistance and rust prevention of the end portion 33.

In the modification of FIGS. 8A and 8B, the second corner portion 22 is superposed on the front side of the first corner portion 14.

The groove forming portion 25 of the second corner portion 22 is constituted by the convex curved wall surface 27 and the inclined wall surface 26. The inclined wall surface 26 is inclined with respect to the front-back direction, that is, with respect to the parting direction of the mold halves 35, 36 such that, toward the front side, the inclined wall surface 26 is inclined away from the first corner portion 14. The inclined wall surface 26 is also in contact with the curved wall surface 15. In the groove 24, the metal coating film 31 is formed at a portion in the curved wall surface 15 that faces the groove 24. The end face of the end portion 33 of the metal coating film 31 is located on the groove forming portion 25, but the end face of the end portion 33 is merely in contact with the groove forming portion 25 and is not bonded thereto.

The part at which the inclined wall surface 26 is in contact with the curved wall surface 15 is defined as the outer edge 22a of the second corner portion 22. The depth D1, which is a dimension in the front-back direction, to the outer edge 22a from the most front side position in the second corner portion 22 is set to a value in the range from 0.15 mm to 1.5 mm. The depth D1 is more preferably set to a value in the range from 0.2 mm to 1.0 mm, and further preferably set to a value in the range from 0.3 mm to 0.8 mm.

In addition, in this modification, the angle θ1 formed by the inclined wall surface 26 with respect to the front-back direction is set to a value in the range from 5° to 15°. The angle θ1 is preferably set to a value in the range from 5° to 10°.

In the modification of FIGS. 8A and 8B, the region between the groove forming portion 25 of the second corner portion 22, which has the inclined wall surface 26 and the curved wall surface 27, and the curved wall surface 15 of the first corner portion 14 constitutes the groove 24. The volume of the groove 24 is larger than the volume of the gap formed between the first corner portion 72 and the second corner portion 74 in the conventional partially plated plastic product, in which the groove 24 is not formed. Thus, even if the plating solution enters the groove 24 when the plating process is performed on the intermediate product 48, the plating solution is easily drained when the intermediate product 48 is taken out from the plating tank 54. Therefore, it is possible to properly form the metal coating film 31 on the outer surface of the first base 11 without exposing the base.

Further, unlike the conventional molding space, the molding space for molding the second corner portion 22 has no space that gradually narrows and hinders flow of molten plastic. Thus, short shots are unlikely to occur. Therefore, it is possible to form the second corner portion 22 having a stable shape, and it is possible to reduce the positional variation of the outer edge 22a as compared to the conventional configuration.

On the other hand, the curved wall surface 15, where the metal coating film 31 is formed in the groove 24, is separated from the second corner portion 22 except for the part in contact with the inclined wall surface 26. Therefore, when being formed, the metal coating film 31 is unlikely to be affected by the second corner portion 22, and the metal coating film 31 is formed in a stable state with respect to the curved wall surface 15.

In addition, the parting line 32 of the metal coating film 31 on the groove forming portion 25 is located in the vicinity of the outer edge 22a. Since the variation in the position of the outer edge 22a is small as described above, the variation in the position of the parting line 32 is also reduced.

In particular, the angle θ1 is set to a small value in range from 5° to 15° and the depth D1 is set to a value in a range from 0.15 mm to 1.5 mm. Thus, even if the position of the parting line 32 varies in a certain range in the front-back direction, the variation has a limited influence on the appearance.

As described above, the metal coating film 31 with small variations in the parting line 32 is formed on the outer surface of the first base member 11 without exposing the base. This improves the appearance of the boundary between the first corner portion 14 and the second corner portion 22.

Furthermore, since the partially plated plastic product 10 is employed as vehicle exterior parts, which originally have large film thicknesses at a portion other than the end portion 33, the following actions and advantages are achieved.

The curved wall surface 15, where the metal coating film 31 is formed, is located at a position away from the anode electrode 56 (see FIG. 8A) further toward the back side than the general wall surface 13 during the plating process. Thus, to the curved wall surface 15, positive charges of the metal component dissolved in the plating solution 55 are less likely to gather than to the general wall surface 13. Therefore, the amount of plating deposited on the curved wall surface 15 is reduced. Further, the plating solution 55 around the first corner portion 14 is more likely to reach the general wall surface 13 than reaching the curved wall surface 15. The plating is first deposited on the general wall surface 13, and accordingly the amount of plating deposited on the curved wall surface 15 thereafter is small.

Thus, it is possible to restrain the end portion 33 from having an excessive thickness on the curved wall surface 15 and having a convex shape. Also, it is possible to suppress the occurrence of a phenomenon in which protrusions are formed in the end portion 33. In this respect also, it is also possible to improve the appearance of the boundary between the first corner portion 14 and the second corner portion 22.

The partially plated plastic product can be employed not only as vehicle exterior parts, but also as vehicle interior parts. In addition, the partially plated plastic product can be employed as decorative articles in fields different from vehicles.

Claims

1. A partially plated plastic product comprising a first base member and a second base member that are made of different plastic materials, wherein

the first base member includes a first corner portion,

the second base member includes a second corner portion,

the first corner portion and the second corner portion are located on a front side of the partially plated plastic product,

the first base member and the second base member are adjacent to each other at least at the first corner portion and the second corner portion,

the first corner portion includes a convex curved wall surface,

only one of the first base member and the second base member includes a metal coating film formed on a region of an outer surface of the base member with which the other base member is not in contact, and

the second corner portion includes a groove forming portion that forms a groove between itself and at least the curved wall surface of the first corner portion.

2. The partially plated plastic product according to claim 1, wherein a width of the groove decreases toward a deepest part of the groove.

3. The partially plated plastic product according to claim 2, wherein

part of a front side surface of the first base member that is adjacent to the first corner portion constitutes a general wall surface of the first base member,

the first corner portion includes an upright wall surface that extends from the curved wall surface in a direction intersecting with the general wall surface,

the groove forming portion includes an inclined wall surface that is inclined with respect to the upright wall surface such that, toward the front side, the inclined wall surface is inclined away from the first corner portion, and

the inclined wall surface is in contact with the upright wall surface.

4. The partially plated plastic product according to claim 3, wherein, in the groove, the metal coating film is formed on the curved wall surface and part of the upright wall surface that faces the groove.

5. The partially plated plastic product according to claim 2, wherein

part of a front side surface of the first base member that is adjacent to the first corner portion constitutes a general wall surface of the first base member,

the first corner portion includes an upright wall surface that extends from the curved wall surface in a direction intersecting with the general wall surface,

the groove forming portion includes an inclined wall surface that is inclined with respect to the upright wall surface such that, toward the front side, the inclined wall surface is inclined away from the first corner portion,

the inclined wall surface is in contact with the curved wall surface, and

the groove is filled with part of the metal coating film.

6. The partially plated plastic product according to claim 3, wherein

part of a front side surface of the second base member that is adjacent to the second corner portion constitutes a general wall surface of the second base member, and

the general wall surface of the first base member and the general wall surface of the second base member are located on a same plane.

7. The partially plated plastic product according to claim 2, wherein

the groove forming portion includes an inclined wall surface that is inclined with respect to a front-back direction such that, toward the front side, the inclined wall surface is inclined away from the first corner portion,

the inclined wall surface is in contact with the curved wall surface,

in the groove, the metal coating film is formed at part of the curved wall surface that faces the groove,

part of the inclined wall surface that is in contact with the curved wall surface is an outer edge of the second corner portion,

a depth, which is a dimension in the front-back direction, to the outer edge from a most front side position on an outer surface of the second corner portion is set to a value in a range from 0.15 mm to 1.5 mm, and

an angle formed by the inclined wall surface with respect to the front-back direction is set to a value in a range from 5° to 15°.