The present invention relates to a wearable article that is worn by a person on his body and touches his skin, such as a case as a component of a wristwatch, a bracelet, or a neckless, a manufacturing method for the wearable article, and a wristwatch structured using the wearable article or the manufacturing method.

Metallic glass materials have conventionally been used as components of industrial products because of having the excellent dimensional accuracy, abrasion resistance, and durability, as described in Patent Literature 1, for example.

On the other hand, the metallic glass materials can be accurately formed to have a complicated shape by a molding process such as the injection molding and therefore have recently been examined to be used for wearable articles such as a main body case of a wristwatch (wristwatch case) or a band of a wristwatch. There are many kinds of metallic glasses and the preferable material that can be stably made into glass is zirconium-based metallic glass, and in particular, Zr-Cu-Al-Ni-based metallic glass is well balanced between the mechanical characteristics and the manufacturability.

In view of the above, using the zirconium-based metallic glass for the wearable article has been suggested.

However, when the metal material containing nickel, such as the zirconium-based metallic glass, touches the skin, nickel is released from the metal material and for some people, may cause a nickel allergy depending on the body constitution. For example, a molded article is formed by molding the Zr-Cu-Al-Ni-based metallic glass and then a nickel release test is carried out (European Standard EN 1811). In this test, the nickel is released from the metal material of the molded article, and the criteria of the standard cannot be satisfied.

In view of this, a nickel-free metallic glass material has been desired but since nickel is a component that largely contributes to the metallic glass formability, it is practically difficult to form the nickel-free zirconium-based metallic glass material.

Patent Literature 1: International Publication WO 2009/069716

The present invention has been made in view of the above conventional circumstances, and an object is to provide a wearable article made of metallic glass, in which the release of nickel can be suppressed, a manufacturing method for the wearable article, and a wristwatch structured using the wearable article or the manufacturing method.

One solution to the problem is a wearable article made of metallic glass containing nickel as a raw material and formed by a molding process to have a body contact part to be in contact with a skin, wherein a foreign substance not containing the raw material of the metallic glass but containing a raw material of a mold used in the molding process has been removed from a surface of the body contact part.

The present invention is structured as described above and therefore can suppress the release of nickel.

• Fig. 1 is a perspective view illustrating one example of a wristwatch as a wearable article according to the present invention, from which a back cover has been detached.
• Fig. 2 is graph expressing the results of the nickel release test on Examples according to the present invention and Comparative Examples according to the conventional technique.
• Fig. 3 is an electron microscope image showing a magnified main part in Comparative Examples according to the conventional technique.
• Fig. 4 is an electron microscope image showing a magnified main part in Examples according to the present invention.

A first feature of the present embodiment is a wearable article made of metallic glass containing nickel as a raw material and formed by a molding process to have a body contact part to be in contact with a skin, wherein a foreign substance not containing the raw material of the metallic glass but containing a raw material of a mold used in the molding process has been removed from a surface of the body contact part.

Here, "wearable article" includes a case as a component of a wristwatch, a back cover of the case, a band for a wristwatch, a bracelet, a neckless, a ring, earrings, pierced earrings, a frame of eyeglasses, and the like.

This structure can prevent the expansion of corrosion that starts from the foreign substance containing the raw material of the mold used in the molding process and that is caused by the influence from the potential difference between the foreign substance and the metallic glass, or the like. As a result, the wearable article having the body contact part that releases less nickel can be provided.

A second feature is a manufacturing method for the wearable article, including a step of performing the molding process using the metallic glass containing nickel as the raw material, and a step of removing the foreign substance from the surface of the body contact part by performing a removal process.

This structure can prevent the expansion of the corrosion from the foreign substance containing the raw material of the mold used in the molding process, because the foreign substance is removed from the surface of the body contact part in the removal process. As a result, the release of nickel from the body contact part can be suppressed.

A third feature is that the removal process includes a polishing process for removing the foreign substance effectively.

A fourth feature is that the foreign substance is removed from the entire surface of a molded article formed by the molding process in order to prevent the expansion of the corrosion effectively.

A fifth feature is that, as a specific aspect with the excellent mechanical characteristics and manufacturability, the metallic glass is zirconium-based metallic glass.

A sixth feature is that, as a specific aspect with the excellent mechanical characteristics and manufacturability, the metallic glass is metallic glass containing zirconium, copper, aluminum, and nickel.

A seventh feature is that the foreign substance is a foreign substance containing iron.

An eighth feature is that a wristwatch is manufactured using the wearable article or the manufacturing method.

Next, preferred examples with the above features will be described in detail with reference to the drawings.

Fig. 1 illustrates a wristwatch A manufactured using a wearable article and a manufacturing method according to the present embodiment.

The wristwatch A includes a wristwatch case 10 and a band 20, which correspond to the wearable article, a watch mechanism 30 housed in the wristwatch case 10, and the like.

The wristwatch case 10 includes a case frame main body 11 and a back cover 12 attached to the back side of the case frame main body 11, which are integrally structured.

The case frame main body 11 is formed to have a frame-like shape with a space penetrating from a front surface side to a back surface side. In a state that the watch mechanism 30 is incorporated, the opening part on the front surface side is covered with a cover glass 13 and the opening part on the back surface side is covered with the back cover 12.

The back cover 12 is a member with a thin-plate shape, and is fixed to the back surface side of the case frame main body 11 with a screw or other fastening means such as engagement or threadening.

This back cover 12 is formed by the molding process using the metallic glass containing nickel as the raw material, and the back surface thereof is a body contact part 12a that will be in contact with the skin.

From the entire surface of the back cover 12 including the body contact part 12a, the foreign substance not containing the raw material of the metallic glass but containing the raw material of the mold used in the molding process is removed by a removal process which will be described below.

Specific examples of the metallic glass include metallic glass containing zirconium (Zr)-copper (Cu)-aluminum (Al)-nickel (Ni).

In this Example, the metallic glass containing Zr55Cu30Al10Ni5 (atm%) was used as the particularly preferable aspect.

Note that the molding process is the process in which the molding is performed by bringing the raw material into contact with the mold, and specific examples of the molding process include an injection molding process, a casting process, a forging process, a pultrusion process, an extrusion process, and a pressing process.

The raw material of the mold used in the molding process is the material a part of which is possibly transferred to the molded article (the back cover 12) to trigger the corrosion of the molded article.

In this example, the raw material of the mold is the metal material containing iron (Fe) as one component, and iron is not contained in the compositions of the metallic glass.

Specific examples of the removal process include polishing processes (including barrel polishing, lap polishing, buff polishing, blast polishing, chemical mechanical polishing, chemical polishing, and other polishing processes), grinding processes (including hairline processes), cutting processes, and the like.

Next, results of performing the nickel release test in the examples with the above structures in comparison to comparative examples will be described in detail.

A test piece in each of Examples 1 to 6 and Comparative Examples 1 to 3 in Fig. 2 is made of the metallic glass as the raw material and the test piece is formed to have a plate shape with approximately the same size as the back cover 12 of the wristwatch A by the injection molding.

The test pieces of Comparative Examples 1 to 3 are made by the injection molding and the removal process is not performed (As-Cast article).

The test pieces of Examples 1 to 3 are made by the injection molding and then the polishing process in which the test piece is brought into sliding contact with a rotating disc-like polishing material.

The test pieces of Examples 4 to 6 are made by the injection molding, the polishing process in which the test piece is brought into sliding contact with a rotating disc-like polishing material, and then the hairline process is performed so that the surface thereof has microscopic unevenness. Namely, these test pieces according to Examples 4 to 6 are the ones having the larger surface area due to the unevenness.

The graph in Fig. 2 shows the results of carrying out the nickel release test based on the European Standard EN 1811 in regard to Examples 1 to 6, and Comparative Examples 1 to 3 by the conventional technique. In this test, each test piece was immersed in a predetermined solution for a predetermined period and then the amount of nickel released per unit area for this period was obtained.

The results indicate that the amount of released nickel in Examples 1 to 6 is remarkably smaller than that in Comparative Examples 1 to 3, and all of them are much lower than the criterion 0.50 µg/cm²/week of EN 1811. In addition, the amount of released nickel is desirably 0.28 µg/cm²/week or less as a criterion in at least a part of the ornament industry, and it is understood that the amount of released nickel is much lower than this criterion.

The amount of nickel release in Comparative Examples 1 to 3 is much more than that in Examples 1 to 6, and the amount of nickel in the two out of the three is more than the criterion.

The comparison between Examples 1 to 3 and Examples 4 to 6 indicates that the amount of released nickel is not remarkably different.

Fig. 3 is a representative image of a part of the surface of the test pieces in Comparative Examples 1 to 3 that is observed with an electron microscope. The image shows that the surface of the test pieces in Comparative Examples 1 to 3 has the projecting foreign substance (attached substance).

The inventors of the present application have conducted the elemental analysis (energy dispersive X-ray analysis) by using the characteristic X-rays emitted from the foreign substance when the substance is irradiated with the electron beam with the use of the known surface analyzer including the electron microscope.

The results from this analysis indicate that this foreign substance includes the component that is not contained in the raw material of the metallic glass but contained in the raw material of the mold used in the molding process (such as iron (Fe)).

Fig. 4 is a representative image of a part of the surface of the test pieces in Examples 1 to 6 that is observed with an electron microscope. In this image, the foreign substance was not found.

The above results indicate that the foreign substance observed in Comparative Examples 1 to 3 (Fig. 3) is the one transferred from a part of the mold used in the molding process.

Moreover, it is considered that in Examples 1 to 6, the foreign substance is removed by the polishing process.

The inventors of the present application estimated that in Comparative Examples 1 to 3, the corrosion expanded starting from the foreign substance so that more nickel was released. In contrast to this, in Examples 1 to 6, the inventors of the present application estimated that much less nickel was released because the foreign substance was removed.

The inventors of the present application also assumed that the increase in surface area due to the foreign substance led to more nickel release. However, this assumption was denied by the fact that there was no remarkable difference in amount of released nickel between Examples 1 to 3 where the polishing process was performed and Examples 4 to 6 where the surface area was increased by the hairline process.

Therefore, according to the Examples, the expansion of corrosion starting from the foreign substance containing the raw material of the mold used in the molding process can be prevented, and as a result, the release of nickel from the body contact part 12a of the back cover 12 can be suppressed.

In the above Examples, the removal process is performed on the entire surface of the back cover 12 as the particularly preferable aspect. However, as another example, the removal process may be performed on only the body contact part 12a of the back cover 12.

In the above Examples, the material, the surface processing method, and the like for the case frame main body 11 and the band 20 are not specified. As another example, however, it is possible that the case frame main body 11 and/or the band 20 is formed in a manner that the metallic glass containing nickel as the raw material is molded and then the aforementioned removal process is performed on at least the surface of the body contact part.

• 10: wristwatch case
• 11: case frame main body
• 12: back cover
• 12a: body contact part
• 20: band
• 30: watch mechanism
• A: wristwatch