EP4663818A1

EP4663818A1 - Plated member and fastener stringer

Info

Publication number: EP4663818A1
Application number: EP23921022.2A
Authority: EP
Inventors: Yuki URITA; Makoto Sasaki; Takuya ABE; Takashi Nakamura; Masayuki IIMORI; Ryosuke TAKEDA
Original assignee: YKK Corp
Current assignee: YKK Corp
Priority date: 2023-02-06
Filing date: 2023-02-06
Publication date: 2025-12-17
Also published as: TW202432901A; JPWO2024166186A1; TWI887832B; JP7847678B2; WO2024166186A1; MX2025009144A; CN120584220A; KR20250145049A

Abstract

Plated article includes a base member (83) including at least one base member metal element; and a plating layer (84) formed on the base member (83). The plating layer (84) includes first and second plating layers (81,82) formed in this order on the base member (83). Each of the first and second plating layers (81,82) includes at least a first metal element of plating layer that is a same metal element as the base member metal element and a second metal element of plating layer that is a different metal element than the base member metal element. Element ratio of the first metal element of plating layer continuously decreases as being away from the base member (83) across a total thickness of at least the first and second plating layers (81,82). Element ratio of the second metal element of plating layer continuously increases as being away from the base member (83) across the total thickness of at least the first and second plating layers (81,82). The second plating layer is visually distinguishable from the first plating layer (81) as a layer containing larger grains than grains of the first plating layer (81) in a first TEM (Transmission Electron Microscope) image.

Description

[Technical field]

The present disclosure is related to a plated article and a fastener stringer.

[Background Art]

Patent literature 1 discloses a plating layer (See symbol 52) formed on a base member made of brass (CuZn) as depicted in its Fig. 23 and as depicted in its Fig. 4, element ratio of base member metal element (Cu,Zn) continuously decreases as being away from the base member, and element ratio of plating layer metal element (Sn) continuously increases as being away from the base member. Fig. 27 of the patent literature 1 discloses a distribution associated with grain area of working example illustrated in the Fig. 23 (See EM in the same figure) of the patent literature 1 where grain areas are distributed in a narrow range.
Patent literature 2 discloses that base members such as buttons are put into a plating tank and plated. In particular, permanent magnets are used to flow magnetic polishing media (magnetic polishing parts) together with buttons or the like, and the base members such as the buttons are plated while being hit by the magnetic polishing media.

[Citation List]

[Patent literature]

[PTL 1] International Publication No. 2018/190202
[PTL 2] International Publication No. 2018/189916

[Summary]

[Technical Problem]

The plating layer disclosed in the patent literature 1 has a higher cohesion with a base member compared with conventional plating layers, and would be useful in various applications. However, a process of electroplating tends to require a longer period of time for a purpose of formation of the plating layer disclosed in the patent literature 1. One reason considered for this is that the growth of the plating layer is impeded as the plating layer is hit by the magnetic polishing media and/or other plated articles to receive impact from them during electroplating (other additional or alternative factors not excluded).
Envisaged is an embodiment where the plating layer disclosed in the patent literature 1 is formed to be thinner, followed by additional common electroplating without the use of magnetic polishing media. However, there is a need to perform different types of electroplating in succession, and thus shortening of time period required for electroplating would be hardly available first of all.
As understandable from the above-described non-limiting exemplary descriptions, further improvement is desired for a plating layer in which respective element ratios of the base member metal element and the plating layer metal element change continuously.

[Solution to Problem]

Plated article according to an aspect of the present disclosure includes a base member including at least one base member metal element; and a plating layer formed on the base member. The plating layer includes first and second plating layers formed in this order on the base member. Each of the first and second plating layers includes at least a first metal element of plating layer that is a same metal element as the base member metal element and a second metal element of plating layer that is a different metal element than the base member metal element. Element ratio of the first metal element of plating layer continuously decreases as being away from the base member across a total thickness of at least the first and second plating layers, and element ratio of the second metal element of plating layer continuously increases as being away from the base member across the total thickness of at least the first and second plating layers. The second plating layer is visually distinguishable from the first plating layer as a layer containing larger grains than grains of the first plating layer in a first TEM (Transmission Electron Microscope) image.
Fastener stringer according to another aspect of the present disclosure includes a fastener tape; and a plurality of fastener elements attached to a side-edge of the fastener tape at a predetermined pitch. Each fastener element of the plurality of fastener elements includes a base member and a plating layer formed on the base member, the base member includes at least one base member metal element. The plating layer includes first and second plating layers formed in this order on the base member. Each of the first and second plating layers includes at least a first metal element of plating layer that is a same metal element as the base member metal element and a second metal element of plating layer that is a different metal element than the base member metal element. Element ratio of the first metal element of plating layer continuously decreases as being away from the base member across a total thickness of at least the first and second plating layers, and element ratio of the second metal element of plating layer continuously increases as being away from the base member across a total thickness of at least the first and second plating layers. The second plating layer is visually distinguishable from the first plating layer as a layer containing larger grains than grains of the first plating layer in a TEM (Transmission Electron Microscope) image.
In some embodiments, the first plating layer is a layer consisting of plural first grains gathering densely, and the second plating layer is a layer consisting of plural second grains gathering densely, the plural first grains each having a width less than 100nm and the plural second grains each having a width greater than 100nm.
In some embodiments, when a rectangular frame is applied to each second grain in the first TEM image and a half of an area of the rectangular frame is determined as an area of the second grain, an average area of the second grains in the first TEM image is equal to or greater than 10000nm², 50000nm² or 100000nm².
In some embodiments, when a rectangular frame is applied to each first grain in a second TEM (Transmission Electron Microscope) image with magnification of the first TEM image or higher than the first TEM image and a half of an area of the rectangular frame is determined as an area of the first grain, an average area of the first grains in the second TEM image is equal to or less than 2000nm² or 1000nm².
In some embodiments, the average area of second grains in the first TEM image is greater than 5 times or 10 times the average area of first grains in the second TEM image, the respective average areas of the first and second grains are in the same unit of mm².
In some embodiments, an area-variance associated with the first grains in the second TEM image is equal to or less than 1/1000 (typically equal to or less than 1/9000, 1/8000, 1/7000, 1/6000, 1/5000, 1/4000, 1/3000, or 1/2000) an area-variance associated with the second grains in the first TEM image, and/or a standard deviation associated with areas of the first grains in the second TEM image is equal to or less than 1/10 (typically equal to or less than 1/60, 1/50, 1/40, 1/30, or 1/20) a standard deviation associated with areas of the second grains in the first TEM image.
In some embodiments, no flat interface is observed between the first plating layer and the second plating layer in the first TEM image and/or no flat interface is observed between the base member and the first plating layer in the first TEM image.
In some embodiments, a thickness of the first plating layer is less than a thickness of the second plating layer.
In some embodiments, a thickness of the first plating layer is equal to or less than 200nm or 150nm.
In some embodiments, a thickness of the second plating layer is in a range between 100nm and 1000nm.
In some embodiments, the first plating layer is formed, in a depth direction directed from a surface of the plated article toward the base member, at a side of the base member relative to an intersection point between a plotting line of element ratio of the first metal element of plating layer and a plotting line of element ratio of the second metal element of plating layer. Distance between the intersection point and the first plating layer may be equal to or greater than 50nm.
In some embodiments, the first metal element of plating layer is copper, the second metal element of plating layer is tin, and the first plating layer includes speculum alloy.
In some embodiments, a multiplicity of dents are formed on a surface of the second plating layer.
In some embodiments, the plated article is a fastener element attached to a fastener tape, the fastener element having at least a pair of legs and an engagement head to which the pair of legs are connected, and the first plating layer formed non-uniformly in separate surfaces of the fastener element.
In some embodiments, the plated article is a fastener element attached to a fastener tape, the fastener element including a surface that is at least partially uneven-finished.
In some embodiments, the fastener element has a main surface oriented along a tape surface for defining a thickness of the fastener tape, and the second plating layer, the first plating layer, and the base member are formed in this order away from the main surface toward the fastener tape.
In some embodiments, the fastener element includes a pair of legs that sandwich the fastener tape, each leg of the pair of legs has a front side connected to a front rim of the main surface and a rear side connected to a rear rim of the main surface, and the second plating layer, the first plating layer, the base member, another first plating layer and another second plating layer are formed in this order between the front side and the rear side.

[Advantageous Effects of Invention]

According to an aspect of the present disclosure, further improvement is provided for a plating layer in which respective element ratios of the base member metal element and the plating layer metal element change continuously.

[Brief Description of Drawings]

[Fig. 1] Fig. 1 is a schematic view of a slide fastener in which each fastener element embodies a plated article according to an aspect of the present disclosure.
[Fig. 2] Fig. 2 is a partially enlarged schematic view of Fig. 1 showing a condition where left and right fastener elements are engaged alternately, and also schematically showing a condition of left and right engaged fastener elements where an engagement protrusion of rear-side fastener element is engaged with an engagement recess of front-side fastener element.
[Fig. 3] Fig. 3 is a schematic perspective view of one fastener element.
[Fig. 4] Fig. 4 is a schematic partial cross-sectional view of the fastener element.
[Fig. 5] Fig. 5 is a schematic graph showing that each element ratio changes in depth direction directed from the surface toward the inside of plated article according to an aspect of the present disclosure.
[Fig. 6] Fig. 6 is a TEM (Transmission Electron Microscope) image of the plated article, which is identical to the one of Fig. 5, in cross section (with observation magnification 50,000 times and observation field 2.5µm×1.9µm), with a dotted line for a boundary between a base member and a first plating layer, a dotted line for a boundary between the first plating layer and a second plating layer, and further a dotted frame outlining a portion to be enlarged in an enlarged image of Fig. 7.
[Fig. 7] Fig. 7 is the enlarged image of the portion in the dotted frame of TEM image shown in Fig. 6.
[Fig. 8] Fig. 8 is a TEM image to which rectangular frames are actually applied for a purpose of calculating areas of second grains.
[Fig. 9] Fig. 9 is a TEM image to which a rectangular frame is actually applied for a purpose of calculating area of second grain.
[Fig. 10] Fig. 10 is a TEM image to which a rectangular frame is actually applied for a purpose of calculating area of first grain.
[Fig. 11] Fig. 11 is a TEM image to which a rectangular frame is actually applied for a purpose of calculating area of first grain.
[Fig. 12] Fig. 12 is a TEM image to which a rectangular frame is actually applied for a purpose of calculating area of first grain.
[Fig. 13] Fig. 13 is a TEM image to which a rectangular frame is applied to a second grain in the vicinity of a surface of the second plating layer far from the first plating layer.
[Fig. 14] Fig. 14 is a graph showing a distribution associated with areas of grains of the plated article which is identical to the one of Figs. 5 and 6.
[Fig. 15] Fig. 15 is an image that images a surface condition of the plated article according to an aspect of the present disclosure.
[Fig. 16] Fig. 16 is an image that images a surface condition of the plated article according to an aspect of the present disclosure.
[Fig. 17] Fig. 17 is an image that images a bottom surface of engagement recess of the plater member according to an aspect of the present disclosure.
[Fig. 18] Fig. 18 is a schematic diagram of an electroplating apparatus according to an aspect of the present disclosure.
[Fig. 19] Fig. 19 is a schematic diagram illustrating that magnetic polishing media move in accordance with alternating magnetic field.
[Fig. 20] Fig. 20 is a schematic diagram of magnetic rotating portion.
[Fig. 21] Fig. 21 is a schematic diagram illustrating that the magnetic rotating portion is housed in a magnetic permeable housing.
[Fig. 22] Fig. 22 is a schematic diagram illustrating a frame for arrangement of anodes.
[Fig. 23] Fig. 23 is a schematic diagram of upside-down inverting unit for inverting a fastener chain upside down.
[Fig. 24] Fig. 24 is a schematic diagram showing a modified example of electroplating apparatus.
[Fig. 25] Fig. 25 is a schematic diagram showing another modified example of electroplating apparatus.
[Fig. 26] Fig. 26 is a schematic diagram showing yet another modified example of electroplating apparatus.
[Fig. 27] Fig. 27 is a schematic diagram of yet another modified example of electroplating apparatus.

[Description of Embodiments]

Hereinafter, various embodiments and features will be described with reference to drawings. A skilled person would be able to combine respective embodiments and/or respective features without requiring excess descriptions, and would appreciate synergistic effects of such combinations. Overlapping descriptions among the embodiments are basically omitted. Referenced drawings aim mainly for describing inventions and are simplified for the sake of convenience of illustration. Each feature should be appreciated as universal feature effective not only to a fastener element disclosed as non-limiting example of plated article of the present application but also to other various metal parts not disclosed herein.
Hereinafter, a plated article according to the present disclosure and features thereof would be discussed in the context of metal-made fastener elements 4a,4b of a slide fastener 1 shown in Fig. 1, but should not be limited to this. The plated article may be embodied as various types of ornament metal parts such as metal-made sliders 7 of slide fastener 1 or metal-made buttons which are irrelevant to the slide fastener, or may be embodied as metal parts in other technical fields like fastening implements such as screws and bolts.
Plated articles according to the present disclosure would be mainly discussed as produced by: transferring a base member through an alternating magnetic field in a plating solution in which magnetic polishing media move randomly, and electrically connecting the base member to a cathode via the magnetic polishing media there to plate the base member: but should not be limited to ones which are plated by an electroplating apparatus described below according to the present disclosure. Specific configurations of electroplating apparatus would be modified in accordance with a type of plated article (e.g. fastener element, slider, or button). Straightly speaking, it would be understood that the plated article according to the present disclosure be produced not only by the presently disclosed electroplating apparatus and method but also by other various electroplating apparatus and methods.
Magnetic polishing media each continues rotating and inverting in accordance with alternating magnetic field. Therefore, the electrical connection of the base member to a cathode electrode via a given magnetic polishing medium would be instantaneous, but the base member would be continuously set to a cathode potential by putting a large number of magnetic polishing media in a plating solution. We consider that the magnetic polishing media collide with the surface of base member and collide with the surface of plating layer that is growing on the base member, causing a distribution of grain size in the plating layer while the plating layer is growing. As described below, a discontinuity is caused in the distribution of grain area in the plating layer according to the present disclosure. One may say that this is not necessarily the best result from a view point of pursuing a highest quality of plating layer, but would be advantageous from a standpoint of dual achievement of a higher cohesion of plating layer and a shortened period of time required for electroplating. This would be clearer from the following descriptions.
TEM image would be used as a cross-sectional image for calculation of grain area. TEM image is captured to show a cross section of a plating layer in a thickness direction of the plating layer. For the TEM images, a transmission electron microscope available from FEI Company Japan Ltd (Model number: TalosF200X) or scanning transmission electron microscope available from Hitachi High-Tech Corporation (Model number: HD-2300A) would be used. Observation magnification is in a range between 50,000 to 1,000,000 times (it should be noted that, in some cases, different apparatuses of transmission electron microscope have different definitions for magnification, even for an equal magnification. Therefore, it would be more appropriate to evaluate a degree of magnification based on an area of observation field in a strict sense. In light of this aspect, magnification field is also noted in the present specification.) The TEM images of Figs. 6 and 7 are obtained by the HD-2300A.
Referring to Figs. 1-3, a slide fastener 1 will be discussed. The slide fastener 1 has a pair of left and right fastener stringers 2a,2b, and a slider 7 that moves forward to couple the stringers and moves rearward to decouple the stringers. The fastener stringer 2a,2b has fastener elements 4a,4b attached to an opposing side-edge of the fastener tape 3a,3b at a predetermined pitch. The slide fastener 1 has front stops at left and right sides which define a frontmost terminal position for the slider 7 and a rear stop that defines a rearmost terminal position for the slider 7 but both can be omitted. The slider 7 may be a common one having a top wing, a bottom wing and an interconnection pillar that interconnects the wings, and thus detail description for this is omitted.
The slide fastener 1 is elongated in the front-rear direction with a predetermined width in the left-right direction, and has a higher softness as a whole. The same applies to the fastener stringer 2a,2b. The slide fastener 1 is attached and fixed to various items such as clothes, bags and shoes, and provides an opening to the item which can be open and closed based on open and closed conditions of the slide fastener 1. The fastener tape 3a,3b is a woven or knitted web with higher softness, and has a side edge to which a core cord CY is situated for securement of the fastener elements 4a,4b. Width directions of the slide fastener 1, the fastener stringer 2a,2b, and the fastener tape 3a,3b are identical to the left-right direction.
The fastener element 4a,4b is produced by electroplating a metal-made base member. The fastener element 4a,4b includes an engagement head 21, and a pair of legs 22,23 that extend in the same direction (along the width direction of the fastener tape 3a,3b) from the engagement head 21 and sandwiches the fastener tape 3a,3b. The engagement head 21 has at its front side an engagement protrusion 46 protruding forward on a central axis CX of the slide fastener 1, and has at its rear side an engagement recess 47 that is recessed forward on the central axis CX. The engagement protrusion 46 is tapered to be narrower in width as extending forward until reaching to its end face 46j. The engagement recess 47 is tapered to be narrower in width as extending forward until reaching to its bottom surface 47j. Complementary shapes of the engagement protrusion 46 and the engagement recess 47 facilitates smooth and firmer engagement between the left and right fastener elements 4a and 4b. The fastener element 4a,4b is not limited to the above-described structure. For example, the engagement head 21 may be structured to have a pair of engagement heads protruding forward and rearward on the central axis CX of the slide fastener 1.
When an observer observes the slide fastener 1 in front (see Fig. 1), alternately arranged main surfaces 51 of the fastener elements 4a,4b would be observed. Each main surface 51 of the fastener element 4a,4b is a surface orientated along (e.g. parallel to) a tape top surface or tape bottom surface, i.e. a tape surface for defining a thickness of the fastener tape 3a,3b. Each main surface 51 of the fastener element 4a,4b may extend from the side-edge of the fastener tape 3a,3b to cross the central axis CX of the slide fastener 1 in the width direction of the slide fastener 1.
The fastener element 4a,4b is produced by electroplating a metal-made base member as described above, and a purpose of the electroplating is to give a desired metal color to the fastener element 4a,4b, particularly to give a desired metal color to the main surface 51. The main surface 51 of the fastener element 4a,4b is uniformly plated, enhancing a quality of appearance of the slide fastener 1. Of course, the electroplating may be performed for additional or alternative purpose such as protection of the base member by the plating layer. Note that the main surface 51 of the fastener element 4a,4b encompasses a main surface portion 51a covering the engagement head 21 and a main surface portion 51b covering the leg 22,23.
As depicted in Figs. 2 and 3, the leg 22,23 has a contact surface 22t,23t that is in contact with the fastener tape 3a,3b, and the main surface 22m,23m that is at the opposite side of the contact surface 22t,23t and positioned remote from the tape surface of the fastener tape 3a,3b. A curved surface is formed in the contact surface 22t,23t to receive the core cord at the side-edge of the fastener tape 3a,3b. The main surface 22m,23m is a flat surface orientated substantially parallel to the tape surface of the fastener tape 3a,3b.
The front side 52 is connected to the front rim of the main surface 22m,23m; the rear side 53 is connected to the rear rim of the main surface 22m,23m; and an end face 54 is formed between the front side 52 and the rear side 53. Any of the front side 52, the rear side 53, and the end face 54 may be a surface that is perpendicular to or substantially perpendicular to a plane where the fastener tape 3a,3b exists. The end face 54 is at a position most inward of fastener tape in the fastener element 4a,4b. Note that, inward of fastener tape indicates a direction directed from a position outside a tape surface of a fastener tape 3a,3b to which fastener elements 4a,4b are attached toward a position on the fastener tape, the direction being orthogonal to the side-edge of the fastener tape 3a,3b.
The engagement head 21 may have top and bottom main surfaces 21m each formed continuously or adjacently to the main surface 22m,23m of the leg 22,23 in the same plane; the end face 46j of the engagement protrusion 46; a first circumferential surface 46k formed about the end face 46j; the bottom surface 47j of the engagement recess 47; and a second circumferential surface 47k formed about the bottom surface 47j. The main surface 21m is a flat surface like the main surface 22m,23m, but should not be limited to this. Needless to say, chamfering can be applied to a verge between surfaces of the fastener element 4a,4b.
In a fastener chain wherein left and right fastener elements 4a,4b are alternately engaged, the main surface 51 is more susceptible to impact from magnetic polishing media during electroplating than the front side 52, the rear side 53, and the end face 54. For example, in adjacent two fastener elements in a single fastener stringer, a front side 52 of a rear-side fastener element and a rear side 53 of a front-side fastener element are opposed to define therebetween a narrow in-liquid space having a narrow width in the front-rear direction. It is likely that the magnetic polishing media in the plating solution move in other in-liquid spaces other than the narrow in-liquid space. Therefore, a plating layer (particularly a first plating layer described below) may be formed finely in the main surface 51 than the front and rear sides 52 and 53 of the fastener element 4a,4b. The same applies to a relationship between the end face 54 and the main surface 51 even though there may be difference in degree of fineness. Comprehensively speaking, a plating layer (particularly a first plating layer described below) may be formed non-uniformly in different surfaces of the fastener element 4a,4b. A first plating layer between the front side 52 and the rear side 53 is formed not uniformly with another first plating layer between the main surface 52 (or the main surface 22m,23m) and the tape surface. Nonuniformity indicates that a thickness of one layer is outside a range between 0.8 times and 1.2 times a thickness of another layer. Typically, a first plating layer directly under the main surface 51 is thicker than first plating layers in other locations, but not necessarily limited to this.
Similar to the above descriptions, the main surface 51 of the fastener element 4a,4b is more susceptible to impact from the magnetic polishing media during electroplating than the end face 46j of the engagement protrusion 46, the first circumferential surface 46k, the bottom surface 47j of the engagement recess 47, and the second circumferential surface 47k. For example, in mutually engaged left and right two fastener elements 4a and 4b of the left and right fastener stringers 2a,2b, the first circumferential surface 46k of the rear-side fastener element and the second circumferential surface 48k of the front-side fastener element are opposed with a small interspace. The same applies to the end face 46j and the bottom surface 47j. It is likely that the magnetic polishing media in the plating solution move in other locations than the above-described small interspace. Therefore, the plating layer (particularly a first plating layer described below) may be formed finely in the main surface 51 than the end face 46j of the fastener element 4a,4b, the first circumferential surface 46k, the bottom surface 47j, and the second circumferential surface 47k. Typically, a first plating layer directly under the main surface 51 is thicker than first plating layers in other locations, but not necessarily limited to this.
Fig. 4 will be referred for further discussion. Fig. 4 schematically illustrates that a plating layer 84 and a metal-made base member 83 are formed in this order in a direction from the main surface 51 of the fastener element 4a,4b toward the inside of the fastener element 4a,4b. The plating layer 84 includes first and second plating layers 81,82 formed in this order on the base member 83. As described below, the first and second plating layers 81 and 82 are visually distinguishable based on difference in grain size observable in a TEM image, but in fact configure a single plating layer produced by a single or common process and apparatus of electroplating. Note that, the plating layer described in the present specification is not necessarily formed as a layer across the entire area of the main surface 51 (unless otherwise specified) and similarly, is not necessarily formed as a flat layer (unless otherwise specified).
With respect to one leg 22,23, the second plating layer 82, the first plating layer 81, and the metal-made base member 83 are formed in this order between the main surface portion 51b of the leg 22,23 and the tape surface of the fastener tape 3a,3b. The plating layer 84 is not formed in the contact surface 22t,23t of the leg 22,23. In cases where the leg 22,23 is cut in a plane parallel to the tape surface, second plating layer, first plating layer, base member, first plating layer and second plating layer are formed in this order between the front side 52 and the rear side 53.
The base member 83 includes one or more base member metal elements. The base member 83 includes in a given case, copper (Cu) as a base member metal element and in another case, includes copper (Cu) and zinc (Zn) as base member metal elements. The former case indicates that the base member 83 is made of copper, and the latter case indicates that the base member is made of brass (CuZn). Embodiments are envisioned where the base member 83 is made of other alternative or additional metal elements. As already established in the patent literature 1, there are a number of candidates for metal elements included in the base member and the plating layer and should not be limited to particular metal elements. Note that the present specification does not focus on trace amount of unavoidable metal element(s) unavoidably contained in metals.
The plating layer 84 includes a first metal element of plating layer that is a same metal element as the base member metal element and a second metal element of plating layer that is a different metal element than the base member metal element. In a case where the base member 83 is made of brass (CuZn), the plating layer 84 includes both of copper (Cu) and zinc (Zn) as the first metal elements of plating layer. In a case where the base member 83 is made of copper (Cu), the plating layer 84 includes copper (Cu) as the first metal element of plating layer. The plating layer 84 includes a second metal element of plating layer that is a different metal element than the base member metal element(s). For example, when a soluble anode including tin (Sn) is used during electroplating, the plating layer 84 includes tin (Sn) as the second metal element of plating layer. Envisioned is that the plating layer 84 includes plural different metal elements as the second metal elements of plating layer.
The above description with respect to the plating layer 84 would equally apply to the first and second plating layers 81 and 82. That is, each of the first and second plating layers 81 and 82 includes a first metal element of plating layer that is a same metal element as the base member metal element and a second metal element of plating layer that is a different metal element than the base member metal element. Just to make sure, in a case again where the base member 83 is made of brass (CuZn), each of the first and second plating layers 81 and 82 includes both of copper (Cu) and zinc (Zn) as the first metal elements of plating layer. In a case where the base member 83 is made of copper (Cu), each of the first and second plating layers 81 and 82 includes copper (Cu) as the first metal element of plating layer. When a soluble anode including tin (Sn) is used during electroplating, each of the first and second plating layers 81 and 82 includes tin (Sn) as the second metal element of plating layer. Envisioned is that each of the first and second plating layers 81 and 82 includes plural different metal elements as the second metal elements of plating layer.
In various preferred embodiments, a thickness of the first plating layer 81 is equal to or less than 200nm or 150nm; and/or a thickness of the second plating layer 82 is preferably in a range between 100nm to 1000nm. The first plating layer 81 may be formed thinner than the second plating layer 82 (in other words, the second plating layer 82 may be formed thicker than the first plating layer 81), which may be advantageous from a standpoint of dual achievement of a higher cohesion of plating layer and a shortened period of time required for electroplating.
Fig. 5 is a schematic graph showing that, in the plating layer 84, element ratios of first metal elements of plating layer continuously decrease as being away from the base member across a thickness of the plating layer 84 (a total thickness of the first and second plating layers 81,82), and an element ratio of second metal elements of plating layer continuously increase as being away from the base member across a thickness of the plating layer (a total thickness of the first and second plating layers 81,82). Fig. 5 shows changes of element ratios in a plating layer of a fastener element plated by an electroplating apparatus described below where a base member is made of brass and a soluble anode includes tin (Sn). In Fig. 5, a dotted line roughly indicates a boundary line L1 between the base member and the first plating layer, and another dotted line roughly indicates a boundary line L2 between the first plating layer and the second plating layer. As a matter of fact, a boundary line between the first plating layer and the base member is observed as an uneven line in accordance with different grain areas in a TEM image (See Fig. 6). The same applies to a boundary line between the first plating layer and the second plating layer.
The element ratios of the first metal elements of plating layer (Cu,Zn in the case of Fig. 5) continuously decrease as being away from the base member, and the element ratio of the second metal element of plating layer (Sn in the case of Fig. 5) continuously increases as being away from the base member. This tendency is consistently observed in the thickness of the plating layer 84 (in the total thickness of the first and second plating layers 81,82).
As appreciated from Fig. 5, in a depth direction directed from a surface of the plated article toward the base member, the first plating layer is formed at a side of the base member relative to an intersection point P1 between a plotting line PL1 of element ratio of the first metal element (Cu in Fig. 5) of plating layer and a plotting line PL2 of element ratio of the second metal element (Sn in Fig. 5) of plating layer. More precisely describing, in a depth direction directed from a surface of plated article toward the base member, the first plating layer is formed at a side of the base member relative to an intersection point P1 between a plotting line PL1 of element ratio of the first metal element of plating layer (Cu) that is identical to the base member metal element (Cu) having the highest element ratio among the base member metal elements (Cu,Zn) and a plotting line PL2 of element ratio of the second metal element of plating layer (Sn). This feature indicates that the first plating layer is formed thinner, and is advantageous from a standpoint of dual achievement of a higher cohesion of plating layer and a shortened period of time required for electroplating.
As appreciated from Fig. 5, an intersection point P2 between a plotting line PL3 of element ratio of the first metal element (Zn) of plating layer that is identical to a base member metal element (Zn) having a lowest element ratio among the base member metal elements (Cu,Zn) and a platting line PL2 of element ratio of the second metal element (Sn) of plating layer may be positioned within a thickness of the first plating layer. This feature indicates that the first plating layer is formed thinner, and is advantageous from a standpoint of dual achievement of a higher cohesion of plating layer and a shortened period of time required for electroplating.
In some cases, a distance D1 between the above-described intersection point P1 and the first plating layer is equal to or greater than 50nm. This feature indicates that the first plating layer 81 is formed thinner, and additionally indicates that element ratio of the second metal element (Sn) of plating layer in the first plating layer 81 is lower. There may be instances where a combination of the first and second metal elements of plating layer produces a unique technical effect. In a non-limiting example where the first metal element of plating layer is copper and the second metal element of plating layer is tin, the first plating layer includes speculum alloy that includes tin having element ratio less than 40%. The speculum alloy has color-stable characteristic in the air, hardness and rust-resistance, thus effecting improved corrosion and wear resistance. Note that, a distance D1 between the above-described intersection point P1 and the first plating layer is typically equal to or less than 100nm.
Figs. 6 and 7 are referred for further discussion. Fig. 6 is a TEM (Transmission Electron Microscope) image of a plated article according to the present disclosure (i.e. the fastener element) in cross section (with observation magnification 50,000 times and observation field 2.5µm×1.9µm). Fig. 7 is an enlarged image of a portion outlined by a dotted frame of TEM image shown in Fig. 6. It is possible to visually distinguish the second plating layer 82 from the first plating layer 81 as a layer having larger grains than grains of the first plating layer 81 (this feature is in contrast to continuity of element ratios of the first and second metal elements of plating layer at both sides of the boundary line L2 between the first and second plating layers 81 and 82 (See Fig. 5)). This facilitates dual achievement of a higher cohesion of plating layer and a shortened period of time required for electroplating. Additionally or alternatively, the second plating layer 82 may have relatively greater degree of malleability as having larger grains than those of the first plating layer 81.
Note that, it would be possible to draw a boundary line L1 that is uneven in accordance with different grain areas of the base member 83 and the first plating layer 81 in TEM image, but a flat interface (which is normally observed in barrel-plating) cannot be observed. It would also be possible to draw a boundary line L2 that is uneven in accordance with different grain areas of the first plating layer 81 and the second plating layer 82, but a flat interface (which is normally observed in barrel-plating) cannot be observed. See Fig. 8 of patent literature 1 for an interface observed in prior art barrel-plating.
The first plating layer 81 is a layer made of plural first grains gathering densely, and the second plating layer 82 is a layer made of plural second grains gathering densely. In the Fig. 6 or 7, it would be possible to visually distinguish the plural first grains each having a width less than 100nm and the plural second grains each having a width greater than 100nm. Difference in width between the first and second grains facilitates dual achievement of a higher cohesion of plating layer and a shortened period of time required for electroplating.
Areas of first and second grains may be calculated based on application of rectangular frame in a TEM image at a desired magnification. Area of one second grain can be calculated as a half of an area of a rectangular frame which is applied to the second grain in a TEM (Transmission Electron Microscope) image (e.g. one shown in Fig. 6) with a desired magnification. Area of one first grain can be calculated as a half of an area of a rectangular frame which is applied to the first grain in a TEM (Transmission Electron Microscope) image (e.g. one shown in Fig. 6 or one with higher magnification) with a desired magnification. Areas of given number of grains typically 10 or 20 grains may be calculated by the above-described method, and an average of the grain areas may be determined. The average area of second grain observed in the TEM image may be equal to or greater than 10000nm² or 50000nm² or 100000nm². The average area of first grain observed in the TEM image may be equal to or less than 1000nm² or 2000nm². The average areas discussed herein are based on results of calculation described above for samples of some plated articles. It should be noted that, as various contours of the first and second grains are observed in TEM image, halves of rectangular frame areas are calculated as grain areas. A TEM image with higher magnification than the TEM image used for calculation of second grain areas may be used for more precise calculation of first grain areas.
Figs. 8 and 9 show conditions of rectangular frame(s) actually applied in TEM image (with observation magnification 50,000 times and observation field 2.5µm×1.9µm) for calculation of second grain area. In the TEM image, a rectangular frame is set such that the four sides thereof touch one second grain therein. For simplified adjustment of position of the rectangular frame, a slight gap may exist between a side of the rectangular frame and the contour of second grain. This may be justified when a correction coefficient is used for calculation of second grain areas as described below. A rectangular frame on TEM image encompasses an entire cross-sectional region of one second grain (in other words, one second grain entirely surrounded by the rectangular frame) which is an object to which the rectangular frame is applied, and one or more cross-sectional partial regions of one or more other second grains around that second grain. Depending on a position of a second grain which is an object to which a rectangular frame is applied, one or more entire or partial cross-sectional regions of one or more first grains may be encompassed. Therefore, a multiplied value of respective lengths of a first side and a second side orthogonal to the first side of rectangular frame may be suitably multiplied by a correction coefficient. This would reduce an effect of noise components included in the multiplied value of respective lengths of the first side and the second side orthogonal thereto of rectangular frame. Note that the correction coefficient may be greater than zero and less than 1, and 0.5 is used in the present disclosure.
Fig. 10 shows a condition where a rectangular frame is actually applied in TEM image (with observation magnification 200,000 times and observation field 0.6µm×0.5µm) for calculation of first grain area. Figs. 11 and 12 show a condition where a rectangular frame is actually applied in TEM image (with observation magnification 500,000 times and observation field 0.3µm×0.2µm) for calculation of first grain area. Areas of first grains in TEM image are calculated similarly by the above-discussed calculation method of second grain area in TEM image. Preferably, TEM image obtained at a higher magnification than a TEM image used for calculation of the second grains is used as the first grains are much smaller than the second grains. Just as a reference, Fig. 13 shows a state where a rectangular frame is applied to a second grain near a surface of the second plating layer remote from the first plating layer.

Tables 1-1 and 1-2 (collectively table 1) and Fig. 14 would be referred for further discussion. In Table 1 and Fig. 14, the grain areas are calculated by the above-discussed rectangular-frame based approach. EM1 in Fig. 14 shows a distribution associated with first grain areas of the plating layer 84 of the plated article shown in Figs. 6 and 7. EM2 in Fig. 14 shows a distribution associated with second grain areas of the plating layer 84 of the plated article shown in Figs. 6 and 7. EM3 in Fig. 14 shows a distribution associated with grain areas of plating layer according to a comparative example of patent literature 1. EM1 in Fig. 14 shows a distribution of 20 plots of first grain areas shown in the table 1. EM2 in Fig. 14 shows a distribution of 20 plots of second grain areas shown in the table 1. EM3 in Fig. 14 shows a distribution of 20 plots of second grain areas shown in the table 1.

[Table 1-1]

	Grain area (nm²)	Vertical width of rectangular frame (nm)	Lateral width of rectangular frame
EM1	3,200	80	80
	4,100	80	103
	3,500	80	88
	1,800	40	90
	800	40	40
	450	30	30
	360	40	18
	90	9	20
	162	8	41
	225	15	30
	563	25	45
	500	25	40
	375	25	30
	250	20	25
	438	35	25
	900	40	45
	200	20	20
	375	25	30
	700	35	40
	900	30	60
EM2	60,000	300	400
	210,000	600	700
	150,000	400	750
	180,000	400	900
	320,000	800	800
	45,000	300	300
	75,000	300	500
	90,000	400	450
	80,000	400	400
	40,000	200	400
	100,000	400	500
	62,500	250	500
	280,000	400	1,400
	70,000	350	400
	82,500	300	550
	45,000	300	300
	60,000	400	300

[Table 1-2]

EM2	35,000	200	350
	61,250	350	350
	37,500	250	300
EM3	150,000	500	600
	450,000	1,500	600
	180,000	900	400
	225,000	900	500
	320,000	1,000	640
	100,000	400	500
	300,000	1,500	400
	40,000	400	200
	7,500	150	100
	20,000	200	200
	75,000	600	250
	375,000	1500	500
	325,000	1300	500
	110,000	550	400
	82,500	550	300
	112,500	450	500
	170,000	850	400
	12,500	250	100
	105,000	300	700
	60,000	300	400

As shown in the table 1, the maximum grain area in the grain area distribution of the first plating layer 81 is 4100 nm². The minimum grain area in the grain area distribution of the second plating layer 82 is 40,000 nm². As such, even though the first and second plating layers 81 and 82 are continuous in the thickness direction of the plating layer 84, there is a large separation with respect to the grain area (the vertical axis of Fig. 8) between the grain area distribution in the first plating layer 81 and the grain area distribution in the second plating layer 82. In some cases, an average area (unit of nm²) of second grain is greater than 10 times (or 50 times) an average area (unit of nm²) of first grain. Difference in area between the first and second grain facilitates dual achievement of a higher cohesion of plating layer and a shortened period of time required for electroplating. [Table 2]

Variance (σ) Ratio of variance

EM1 6.2×10⁵ -

EM2 6.7×10⁹ 9.2×10^-5

EM3 1.7×10¹⁰ 3.7×10^-5
Table 2 shows variances of EM1-EM3 which are calculated based on the grain areas shown in the table 1. Average grain area can be calculated based on a formula of numeral 1. Variance can be calculated based on a formula of numeral 2. Note that, from the convenience of calculation, a value of variance is expressed in exponential notation, and its rational number is expressed in two digits interposing a decimal point. Two digits after the decimal point are rounded off. $\bar{x} = \frac{1}{n} \sum_{i = 1}^{n} x_{i}$
Here, n indicates a sample number, and x_i indicates an observed value. $σ^{2} = \frac{1}{n} \sum_{i = 1}^{n} {(x_{i} - \bar{x})}^{2}$
Here, n indicates a sample number, and x_i indicates an observed value.
The variance of grain area distribution in the first plating layer 81 (=6.2×10⁵) is about 1/10000 of the variance of grain area distribution in the second plating layer 82 (=6.7×10⁹), and satisfies a condition of 1/1000 or less (may satisfy any one of conditions selected from 1/9000 or less, 1/8000 or less, 1/7000 or less, 1/6000 or less, 1/5000 or less, 1/4000 or less, 1/3000 or less, and 1/2000 or less). This indicates that grains in the first plating layer 81 are formed densely compared with grains in the second plating layer 82.
Variance ratio shown in the row of EM2 in the table 2 is calculated by dividing the variance of EM1 by the variance of EM2. Variance ratio shown in the row of EM3 in the table 2 is calculated by dividing the variance of EM1 by the variance of EM2. From these values of variance ratio, it would be possible to understand that grains in the first plating layer 81 are formed densely. [Table 3]

Standard deviation

EM1 1,163

EM2 79,897

EM3 126,724
Table 3 shows standard deviations calculated from the variances shown in the Table 2. Standard deviation (=1163) associated with grain areas in the first plating layer 81 is about 1/69 of standard deviation (=79897) associated with grain areas in the second plating layer 82, and satisfies a condition of 1/10 or less (may satisfy any one of conditions selected from 1/60 or less, 1/50 or less, 1/40 or less, 1/30 or less, and 1/20 or less). This indicates that grains in the first plating layer 81 are formed densely compared with grains in the second plating layer 82.
The second plating layer 82 may be formed even thicker so that the average area of second grains becomes even greater than the average area of first grains. Similarly, the variance of second grain areas may become much greater than the variance of first grain areas (the same applies to the standard deviation). In this regard, a maximum value of thickness of the second plating layer may be equal to or less than 15 times or 10 times or 5 times a maximum value of thickness of the first plating layer. In the observed plated article in the table 1 and Fig. 14, a thickness of the first plating layer 81 is in a range between 50nm and 150nm, and a thickness of the second plating layer 82 is in a range between 300nm and 500nm. A maximum value of thickness of the second plating layer 82 is less than 5 times a maximum value of thickness of the first plating layer 81.
Note that, it is impractical to observe and calculate all areas of the first and second grains contained in a given plated article. Therefore, for a purpose of calculating an average of grain area, the average area may preferably be calculated based on a predetermined number (e.g. 18, 20, 30, 40, or 50) of grains randomly selected in a TEM image at a desired magnification as described above. The TEM image may be sectioned into plural sections for the random selection, and an equal number of grains may be selected in the respective sections. Additionally or alternatively, a rule may be adopted where a gain having a greater area than a grain selected at the first time is selected at the second time, and a grain having a lesser area than the grain selected at the second time is selected at the third time. More accurate evaluation would be enabled by increasing the number of samples.
Figs. 15-17 would be referred for further discussion. Fig. 15 relates to a case where the second metal element of plating layer is tin, and Figs. 16 and 17 relate to a case where the second metal element of plating layer is copper (the base member metal element is a metal element other than copper). From these images (particularly Fig. 16), what can be seen is that the surface of the fastener element is uneven-finished such that a plurality of dents are formed on the surface of the fastener element. The plating layer 84 may be formed at the outermost layer without forming an additional plating layer onto the plating layer 84 in the plated article so that the uneven-finished pattern formed during the electroplating (as being hit by magnetic polishing media) would be exposed. In a case where the plated article is a fastener element, an optical effect of reduced degree of gloss on its main surface may be obtained additionally to the design effect of the uneven pattern. Note that the dents on the surface of the fastener element should not be limited to be formed to produce the uneven surface. As shown in Fig. 17, no dent is formed on the bottom surface 47j of the engagement recess 47 of the fastener element. This proves that the fastener elements plated by the presently disclosed electroplating were in a configuration of fastener chain, facilitating efficient electroplating. The bottom surface 47j of the engagement recess 47 is normally not seen by users, and thus design aspect of the fastener element would not be deteriorated even if the pattern is not formed there.
Figs. 18-27 would be referred hereinafter to describe an apparatus and process of electroplating. In the descriptions regarding the apparatus and process of electroplating, fastener elements 4a',4b' basically match base members 83 of the above-described fastener elements 4a,4b. Therefore, it should be noted that a plating layer is described to be formed on the fastener element and not included in the fastener element.
From a standpoint of demand of high production efficiency of slide fastener 1, the base members of the fastener elements are plated in a condition where the fastener elements 4a',4b' are attached to the fastener tapes 3a,3b (e.g. in a configuration of fastener stringer or fastener chain), unlike respective electroplating for respective fastener elements 4a',4b'. The following description describes that electroplating is performed with respect to a fastener chain, but replacement of the fastener chain to a fastener stringer would be understandable.
Exemplary production method includes following processes (e.g. see Figs. 18 and 19 together): a process of applying a voltage between one or more cathodes 10 and one or more anodes 20 which are at least partially immersed in an electrolyte in a plating tank 30; a process of generating an alternating magnetic field in the electrolyte when or during a period of time in which the voltage is applied between the one or more cathodes 10 and the one or more anodes 20; a process of continuously transferring a fastener chain 1' in a predetermined travel path 80 such that at least the fastener elements 4a',4b' of the fastener chain 1' travel through the alternating magnetic field; and a process of allowing magnetic polishing media 9 to move in accordance with the alternating magnetic field, electrically connecting the fastener elements 4a',4b' to the cathode 10 via the magnetic polishing media 9, and allowing the magnetic polishing media 9 to collide with plating layers growing on the fastener elements 4a',4b'.
The transfer speed of the fastener chain 1' may be equal to or greater than 10M per minute or may be 15M per minute or 20M per minute. Such a high-speed transfer of the fastener chain 1' allows not only a high production rate but also facilitates formation of bulky grains in the second plating layer 82 compared with grains in the first plating layer 81 as shown in Figs. 6-8.
The process of generating the alternating magnetic field in the electrolyte may include rotating one or more magnetic rotating portions 60 (see Fig. 20) where different magnetic poles are alternately arranged in the rotational direction. This may be housed in a sealed magnetic permeable housing 70 in a rotatable manner (see Fig. 21). Plural supporting members 78 are arranged on the external side of the magnetic permeable housing 70 so as to support the fastener chain 1' (see Fig. 18), thereby defining the transfer passage. The magnetic rotating portion 60 rotates at high speed inside of the magnetic permeable housing 70 and, a magnetic pole nearest from a given fastener element 4a',4b' continuously alternates between N-pole and S-pole as depicted in (a) and (b) of Fig. 19. As such, the magnetic polishing media 9 randomly move to hit the fastener elements 4a',4b' moving in the transfer passage and the plating layers growing on the fastener elements 4a',4b'.
More concreate descriptions follow hereinbelow. As depicted in Fig. 18, the electroplating apparatus 100 has a plating tank 30, a conveyor mechanism 40, an alternating magnetic field generator 50, and a travel path 80 for the fastener chain 1'. The fastener chain 1' moves into the plating tank 30 from the outside owing to rollers 41,42 of the conveyor mechanism 40, and exits from the plating tank 30 to the outside owing to rollers 43,44 of the conveyor mechanism 40.
The plating tank 30 stores the electrolyte solution 35 in which the one or more cathodes 10 and the one or more anodes 20 are immersed. The plating tank 30 is an insulator housing having a bottom plate 31 and a side plate 32. The electrolyte solution 35 in the plating tank 30 may be a cyanide plating solution for example, and may be circulated between the bath and an external auxiliary bath. For a purpose of reduction of environmental load, a plating solution not including specific hazardous substances such as cyan, chrome and selenium may be preferably used. The cathode 10 and the anode 20 are connected to a DC power source E1 and a voltage is applied between them. Voltage applied condition can be controlled by turning a switch SW ON or OFF. The anode 20 may be a soluble or insoluble anode. The metal element of the anode 20 may be suitably selected in accordance with the second metal element of plating layer. The cathode 10 is positioned away from the anode 20 in the electrolyte solution 35 in order to supply electrons to the fastener elements 4a' and 4b' (in order to set the fastener elements 4a' and 4b' at the cathode potential).
The alternating magnetic field generator 50 generates an alternating magnetic field in the electrolyte solution 35 in the plating tank 30. The alternating magnetic field indicates a magnetic field altering in magnitude and direction along the time. The travel passage 80 for the fastener chain 1' is established such that the fastener chain 1' is arranged in the alternating magnetic field generated by the alternating magnetic field generator 50. In a situation where the generation of the alternating magnetic field and the travel of the fastener chain 1' occur simultaneously or in a same time window, the fastener elements 4a',4b' of the fastener chain 1' pass through the alternating magnetic field being generated by the alternating magnetic field generator 50.
The cathode 10 is provided to allow the magnetic polishing media to move (e.g. rotate) in accordance with the above-described alternating magnetic field at a space between the cathode 10 and the fastener element 4a',4b' of the fastener chain 1' supported by the supporting members 78, and to be electrically connectable to the fastener elements 4a' and 4b' via the magnetic polishing media. In other words, (i) provided is a space, where the magnetic polishing media move in accordance with the alternating magnetic field, between the cathode 10 and the fastener element 4a',4b' of the fastener chain 1' being supported by the supporting members 78; and (ii) this space is configured to allow the fastener element 4a',4b' to be electrically connected to the cathode 10 via the magnetic polishing media and to allow the magnetic polishing media to hit the plating layer growing on the fastener element 4a',4b'.
The above configuration ensures simultaneous occurrence of the growth of plating layer on the fastener element 4a',4b' and collision of the magnetic polishing media against the plating layer. This facilitates the formation of plating layer with sufficient quality (e.g. sufficient tolerance against processing). Also, when running the fastener chain continuously or intermittently in the travel passage 80 defined by the supporting members 78, the process of electroplating can be performed efficiently.
The supporting members 78 may be provided to regulate the position and orientation of the fastener chain 1' such that an elongation direction of the fastener chain 1' is oriented along a predetermined direction in which different magnetic poles are alternately arranged for generating the alternating magnetic field (e.g. a circumferential direction and/or a rotational direction of a magnetic rotating portion 60 described below), and such that the fastener chain 1' faces the magnetic pole in the flat posture in its width direction. This facilitates the formation of plating layer having uniform quality and/or thickness.
The alternating magnetic field generator 50 includes a motor 61 and a magnetic rotating portion 60 revolved by the motor 61. The motor 61 may be a DC or AC motor, for example. In the magnetic rotating portion 60, different magnetic poles (i.e. N-pole and S-pole) are arranged alternately in the rotational direction. Permanent magnet or electromagnet or combination of such magnets can be used for the magnetic pole. In the illustrated case of Fig. 20, permanent magnets are used for the magnetic poles. The magnetic rotating portion 60 has a rotatable rotating body 63 fixed to a rotational axis 62 of the motor 61, and a plurality of permanent magnets 64 arranged on the outer surface of the rotating body 63. The rotating body 63 is a hollow cylinder made of stainless-steel, for example. The permanent magnet 64 may be a rare-earth magnet such as neodymium magnet, but other types of magnets can be employed. It is not a requisite to provide one motor 61 corresponding to one magnetic rotating portion 60. Appropriate drivetrain may transmit the output of motor 61 to a plurality of magnetic rotating portions 60. Note that the rotational axis 62 of the motor 61 may be secured to an aperture in the bottom plate 31 of the plating tank 30 via a waterproof bearing.
The permanent magnets 64 are arranged such that S-pole and N-pole are arranged alternately in the rotational direction of the magnetic rotating portion 60 (See Fig. 20). When the magnetic rotating portion 60 rotates as the motor 61 operates, the magnetic rotating portion 60 is alternately switched between S-pole and N-pole when viewed from a prefixed position radially outward of the magnetic rotating portion 60. The magnetic polishing media (e.g. pin media) at a given position radially outward the magnetic rotating portion 60 rotates in accordance with the change of the magnetic pole (nearest one from the magnetic polishing media) and flows in the rotational direction of the magnetic rotating portion 60. The rotational speed of the magnetic rotating portion 60 may be in a range of 100-4,000 rpm, for example.
As depicted in Fig. 20, in the outer surface of the magnetic rotating portion 60, N-pole arrangement zones z1,z3,z5 with the arrangement of the permanent magnets 64 having N-pole directed outward and S-pole arrangement zones z2,z4 with the arrangement of the permanent magnets 64 having S-pole directed outward may be alternately arranged in the rotational direction of the magnetic rotating portion 60. In Fig. 20, the N-pole arrangement zones z1,z3,z5 and the S-pole arrangement zones z2,z4 extend straight vertically in parallel to the rotational axis of the magnetic rotating portion 60, but should not be limited to such manner. In some cases, sinking of the magnetic polishing media due to gravity is considered, and the N-pole arrangement zone z1,z3,z5 and the S-pole arrangement zone z2,z4 obliquely extend along a vertical direction not in parallel to the rotational axis of the magnetic rotating portion 60 or extend in zigzag along a vertical direction not in parallel to the rotational axis of the magnetic rotating portion 60.
The electroplating apparatus 100 further includes a magnetic flux permeable housing 70 in which the magnetic rotating portion 60 is housed rotatably in a sealed condition. The magnetic flux permeable housing 70 transmits magnetic flux directed from the N-pole to S-pole of the permanent magnet 64 of the magnetic rotating portion 60 therein, allowing formation of the magnetic field outside the magnetic flux permeable housing 70. The magnetic flux permeable housing 70 is kept stationary at a given location without rotating together with the magnetic rotating portion 60 as the motor 61 operates and for example, is coupled to the rotational axis 62 via waterproof bearings (at its bottom plate and its top plate). By providing the magnetic flux permeable housing 70, the magnetic rotating portion 60 can be protected from the electrolyte solution 35 and/or rotational resistance can be reduced for the magnetic rotating portion 60. The magnetic flux permeable housing 70 is made of a resin such as polypropylene or acryl or vinyl chloride or the like, for example.
As the one or more supporting members for supporting the fastener chain 1', the plurality of supporting members 78 is arranged on the outer surface of the magnetic flux permeable housing 70. This regulates the position and posture of the fastener chain 1' and defines the travel passage 80. Preferably, the fastener chain 1' is supported in a flat posture by the supporting member (e.g. the supporting members 78). The fastener chain 1' can run around the magnetic rotating portion 60, in particular run circumferentially at position radially outward of the rotational axis 62 of the magnetic rotating portion 60. Density of magnetic flux decreases as being away radially outward from the magnetic rotating portion 60, but the fastener chain 1' can run near the magnetic rotating portion 60 as the magnetic flux permeable housing 70 is provided with the supporting members 78. The magnetic polishing media can move largely in accordance with the alternating magnetic field in a space between the magnetic flux permeable housing 70 and the fastener chain 1', and the magnetic polishing media can hit the plating layer hard. In some cases, the supporting members 78 are attached to the outer surface of magnetic flux permeable housing 7 so as to define a spiral travel passage 80 for the fastener chain 1'. The travel passage 80 is configured in spiral so that upsizing of the electroplating apparatus 100 is avoided.
Each supporting member 78 is a L-shaped member and in particular, has a first bar 78a extending radially outward of the rotational axis 62 of the magnetic rotating portion 60, and a second bar 78b extending upward with a predetermined interspace against the outer surface of the magnetic flux permeable housing 70. The first bar 78a prevents the fastener chain 1' from sinking in the electrolyte solution 35 due to gravity. The second bar 78b prevents the fastener chain 1 from collapsing in a direction away from the outer surface of the magnetic flux permeable housing 70 due to gravity or magnetic polishing media or water flow or the like. The supporting members 78 may be secured to the magnetic flux permeable housing 70 in its periphery by any methods such as use of screw or adhesive.
The cathode 10 can be arranged on the outer surface of the magnetic flux permeable housing 70. The cathode 10 may be provided to extend along the travel passage for the fastener chain 1'. Owing to this, the electrical connection between the cathode 10 and the fastener element 4a',4b' via the magnetic polishing media is expected to be improved. In some cases, the cathode 10 is provided in spiral around the magnetic flux permeable housing 70 corresponding to the spiral travel passage 80 for the fastener chain 1'. Additionally or alternatively to this, the cathode 10 is positioned such that the fastener element 4a',4b' of the fastener chain 1' faces the cathode 10 while the fastener chain 1' runs in the travel passage 80. Note that, there will a state in which the permanent magnet 64, the magnetic flux permeable housing 70, the cathode 10, the magnetic polishing media and the fastener element 4a',4b' are arranged on a same radial line with respect to the rotational axis of the magnetic rotating portion 60.
In a case where the cathode 10 is provided on the outer surface of the magnetic flux permeable housing 70, an induced electromotive force is caused in the cathode 10 due to the rotation of the magnetic rotating portion 60, and an induced current flows in the cathode 10. To minimize this effect, the cathode 10 is provided not as a cylinder but as a line on the outer surface of the magnetic flux permeable housing 70. Magnetic flux linkage with respect to the cathode 10 is reduced, suppressing the induced electromotive force and the induced current. Note that the spiral cathode 10 can be constructed by spirally winding the linear cathode 10 around the outer surface of the magnetic flux permeable housing 70. The linear cathode 10 can be provided on the outer surface of the magnetic flux permeable housing 70 in a manner other than the spiral manner. The cathode 10 can be secured to the outer surface of the magnetic flux permeable housing 70 by ways of screw or adhesive or fitting or the like.
In a case where the linear or spiral cathode 10 is provided, the length of the cathode 10 may be longer. For a purpose of stabilized potential of the cathode, in one magnetic flux permeable housing 70, the cathode 10 may have a plurality of contacts with the DC power source E1, or the cathode 10 may be divided and the divided cathodes may have respective contacts with the DC power source E1.
Frame 72 can be used to position the anode 20 near the travel passage 80 for the fastener chain 1' (See Fig. 22). A plurality of anodes 20 may be attached to the frame 72 directly or indirectly via a cage or the like so that the anodes 20 can be deployed at different locations along the travel passage 80 for the fastener chain 1'. This reduces imbalance in metal ion density along the travel passage 80 for the fastener chain 1'. For example, mesh cages are attached to the frame 72 and the metal plates (that function as the anode 20) are placed in the cage.
The frame 72 is positioned radially outward of the magnetic flux permeable housing 70 with respect to the rotational axis 62 of the magnetic rotating portion 60. The frame 72 is a cylindrical tubular mesh having cross members 73 aligned vertically with interspaces and vertical members 74 linking the cross members 73 in the vertical direction. The frame 72 is constructed so as not to interfere with the travel passage 80 for the fastener chain 1'. Metal ions eluted from the anode 20 can reach, through the openings in the mesh structure of the frame 72, the fastener element 4a',4b' of the fastener chain 1' placed in the travel passage 80. As would be appreciated by a skilled person, the anodes 20 can be positioned near the travel passage 80 for the fastener chain 1' without using the frame 72.
Function of the magnetic polishing media will be further discussed with reference to Fig. 19. In a state shown in Fig. 19(a), the N-pole arrangement zone of the magnetic rotating portion 60 is positioned inward of a given position in the periphery of the magnetic flux permeable housing 70. In a state shown in Fig. 19(b), the S-pole arrangement zone of the magnetic rotating portion 60 is positioned inward of the given position in the periphery of the magnetic flux permeable housing 70. There is an appropriate amount of magnetic polishing media 9 in the space between the cathode 10 and the fastener element 4a',4b' in both states of Figs. 19(a) and 19(b) and here, the magnetic flux is illustrated by dash line.
In a course of change of the direction of the magnetic flux from Fig. 19(a) to Fig. 19(b), each magnetic polishing medium 9 rotates and moves. The fastener element 4a',4b' may be electrically connected to the cathode 10 via the media before or after the process or in the entire process regardless of the change in orientation and position of each magnetic polishing medium 9. When rotating, some magnetic polishing media 9 collide with the plating layer growing on the fastener element 4a',4b'. Even if some fastener elements 4a',4b' were not electrically connected to the cathode 10 via the magnetic polishing media 9, the fastener chain 1' may be electrically connected to the cathode 10 via other fastener elements 4a',4b'.
The magnetic polishing media 9 may be used to facilitate the transfer of the fastener chain 1', not necessarily limited to this though. For example, the rotational direction of the magnetic rotating portion 60 and the travel direction of the fastener chain 1' around the magnetic rotating portion 60 may be set to match one another. In addition to rotating in accordance with the alternating magnetic field, the magnetic polishing media 9 is attracted to the permanent magnet 64 of the magnetic rotating portion 60 and flows in the same direction as the magnetic rotating portion 60. This flow of magnetic polishing media 9 pushes the fastener chain 1', allowing the fastener chain 1' to smoothly run in the same direction.
The fastener element 4a',4b' of the fastener chain 1' has a first surface 5 facing the cathode 10 and a second surface 6 facing the opposite side of the cathode 10 (See Fig. 19). Assuming that the anode 20 is positioned radially outward than the fastener chain 1' from the magnetic flux permeable housing 70 and the magnetic polishing media are distributed equally in its amount at both sides of the first surface 5 and the second surface 6 of the fastener element 4a',4b', the growth speed of plating layer on the second surface 6 of the fastener element 4a',4b' would be greater than the growth speed of plating layer on the first surface 5 of the fastener element 4a',4b'. The fastener chain 1' may be preferably inverted upside down in a travel passage for the fastener chain 1' in order to suppress a thickness difference of plating layer in the front and back sides of the fastener element 4a',4b'.
In a case illustrated in Fig. 18, there are two alternating magnetic field generators 50 in the plating tank 30. An upstream spiral travel passage is arranged around the magnetic flux permeable housing 70 of the upstream alternating magnetic field generator 50. A downstream spiral travel passage is arranged around the magnetic flux permeable housing 70 of the downstream alternating magnetic field generator 50. The upside-down inverting unit 90 for the fastener chain 1' is provided between those spiral travel passages.
In a case illustrated in Fig. 23, the upside-down inverting unit 90 just has two guide rollers 91, 92. The upside-down inversion of the fastener chain 1' is achieved by inverting the travel direction of the fastener chain 1' between the upstream magnetic flux permeable housing 70 and the downstream magnetic flux permeable housing 70. That is, when viewing the plating tank 30 from above as depicted in Fig. 23, the fastener chain 1' runs clockwise in the upstream spiral travel passage, and runs counter-clockwise in the downstream spiral travel passage. As such, the fastener chain 1' is inverted upside down, facilitating equal thickness of plating layer at front and back sides of the fastener element 4a',4b'. Note that the inverting the fastener chain1 upside down may be performed by other various methods.
Operation of the electroplating apparatus 100 will be discussed with a focus on a portion of the fastener chain 1'. Firstly, as the fastener chain 1' travels, a portion of the fastener chain 1' reaches the travel passage 80 in the electrolyte solution 35 as being guided by the rollers 41,42. Before the portion of the fastener chain 1' enters into the travel passage 80, the magnetic rotating portion 60 is rotated based on actuation of the motor 61 so that the alternating magnetic field is effected around the magnetic rotating portion 60. The travel passage 80 of the fastener chain 1' is arranged in the alternating magnetic field and the magnetic polishing media 9 are moving therein. Furthermore, the DC power source E1 is applying a voltage across the cathode 10 and the anode 20.
When the portion of the fastener chain 1' runs in the travel passage 80, the fastener elements 4a',4b' thereof are electrically connected to the cathode 10 provided at the outer surface of the magnetic flux permeable housing 70 via the magnetic polishing media 9. Also, the magnetic polishing media 9 repeats colliding with the plating layer being formed on the fastener element 4a',4b'. In a time window in which the portion of the fastener chain 1' runs from the bottom end toward the top end of the spiral travel passage 80, the growth of the plating layer and the collision of the magnetic polishing media 9 with the plating layer occur continuously. Accordingly, upsizing of the electroplating apparatus 100 may be avoided and formation of the plating layer with sufficient thickness may be facilitated.
The portion of the fastener chain 1' would be then inverted upside down and runs in the opposite direction in the next spiral travel passage 80 i.e. from its top end toward the bottom end. Similar to above, in this time window, the growth of the plating layer and the collision of the magnetic polishing media 9 with the plating layer occur continuously. Accordingly, the plating layer is formed on the front and back sides of the fastener element 4a',4b' of the fastener chain 1'. After passing through the spiral travel passage 80, the portion of the fastener chain 1' exits the electrolyte solution 35 as being guided by the rollers 43, 44.
Note that the metal ions are deposited on the contacting portions between the fastener elements 4a' and 4b' so that the plating layer is formed thereon. During electroplating, the line of the fastener elements 4a' and 4b' is electrically connected to the cathode 10 continuously along the elongation direction of the fastener chain 1', and thus suppressing that a potential slope is caused in the line of the fastener elements 4a' and 4b' along the elongation direction of the fastener chain 1'. Sequencer can be used for turning each motor 61 ON/OFF and turning the switch SW ON/OFF. The sequencer may control the transfer of the fastener chain for the start or stop operation.
Embodiment in which two alternating magnetic field generators 50, two spiral travel passages and one upside-down inverting unit 90 are provided has been described mainly with reference to Fig. 18 in the above description but, envisioned is an embodiment where just one alternating magnetic field generators 50 and just one spiral travel passage are provided. The travel passage 80 for the fastener chain 1' is not necessarily limited to the spiral configuration and may have a linear or zigzag configuration or the like. It would also be possible to arrange the fastener chain 1' to meander across the plurality of magnetic flux permeable housings 70, and repeating this arrangement along the rotational axis of the magnetic rotating portion 60.
Hereinafter, variants will be discussed with reference to Figs. 24-27. Figs. 24 and 25 show an embodiment where four alternating magnetic field generators 50, four spiral travel passages and two upside-down inverting units 90 are provided. In Fig. 24, the fastener chain 1' runs in the 1^st spiral travel passage clockwise upward, runs the 2^nd spiral travel passage counterclockwise downward, runs the 3^rd spiral travel passage counterclockwise upward, and runs the 4^th spiral travel passage clockwise downward. In Fig. 25, the fastener chain 1' runs in the 1^st spiral travel passage counterclockwise upward, runs the 2^nd spiral travel passage clockwise downward, runs the 3^rd spiral travel passage clockwise upward, and runs the 4^th spiral travel passage counterclockwise downward. Sufficient thickness of plating layer may be ensured even if the transfer speed of the fastener chain 1' is set faster, owing to the arrangement of 4 or more alternating magnetic field generators 50 and 4 or more spiral travel passages.
Figs. 26 and 27 disclose an embodiment where the posture of the fastener chain 1' is maintained by the rollers 41,42 of the conveyor 40 not by the supporting member 78 (that is, the rollers 41,42 of the conveyor 40 function as a supporting member for the fastener chain 1'). Even in such a case, the above-described effects would be similarly obtained within a consistent extent.
The plated article shown in Figs. 6-8 is one obtained by using an electroplating apparatus having a same configuration as that shown in Fig. 24. However, various modifications discussed above can be possible for the electroplating apparatus, and thus it should be appreciated that there is no limitation on the configuration of the electroplating apparatus.

Working example

The electroplating apparatus shown in Fig. 24 of the present application was used to form plating layers on fastener elements in a fastener chain. The rotational speed of the magnetic rotating portion was 400 rpm. The travel speed of the fastener chain was 5m/minute. The voltage of power supply was 1V, and electrical current of 10A flowed the respective cathodes. Time period of electroplating per a fastener element was 15 minutes. There were media of 9g thrown-in per 1L of electrolyte. The media was pin media having a length of 5mm and a diameter of 0.8mm. The base member of the fastener element was made of brass, and tin bars were used as soluble anode. Accordingly, a first plating layer having a thickness in a range between 50nm and 150nm and a second plating layer having a thickness in a range between 300nm and 500nm were formed. Uneven pattern was formed on the outermost surface of the second plating layer due to impact of the magnetic polishing media. TEM images were ones as shown in Fig. 6.
Based on the above teachings, a skilled person in the art would be able to add various modifications to respective embodiments and respective features. Reference codes in Claims are just for reference and should not be referred for the purpose of narrowly construing the scope of claims.

[Reference code]

2a :: Fastener stringer
2b :: Fastener stringer
3a :: Fastener tape
3b :: Fastener tape
4a :: Fastener element
4b :: Fastener element
81 :: First plating layer
82 :: Second plating layer
83 :: Base member
84 :: Plating layer

Claims

A plated article comprising:
a base member (83) including at least one base member metal element;
and

a plating layer (84) formed on the base member (83), the plating layer (84) including first and second plating layers (81,82) formed in this order on the base member (83), each of the first and second plating layers (81,82) including at least a first metal element of plating layer that is a same metal element as the base member metal element and a second metal element of plating layer that is a different metal element than the base member metal element, wherein

an element ratio of the first metal element of plating layer continuously decreases as being away from the base member (83) across a total thickness of at least the first and second plating layers (81,82),

an element ratio of the second metal element of plating layer continuously increases as being away from the base member (83) across the total thickness of at least the first and second plating layers (81,82), and

the second plating layer (82) is visually distinguishable from the first plating layer (81) as a layer containing larger grains than grains of the first plating layer (81) in a first TEM (Transmission Electron Microscope) image.
The plated article of Claim 1, wherein the first plating layer (81) is a layer consisting of plural first grains gathering densely, the plural first grains each having a width less than 100nm, and
the second plating layer (82) is a layer consisting of plural second grains gathering densely, the plural second grains each having a width greater than 100nm.
The plated article of Claim 2, wherein when a rectangular frame is applied to each second grain in the first TEM image and a half of an area of the rectangular frame is determined as an area of the second grain, an average area of the second grains in the first TEM image is equal to or greater than 10000nm², 50000nm² or 100000nm².
The plated article of Claim 3, wherein when a rectangular frame is applied to each first grain in a second TEM (Transmission Electron Microscope) image with magnification of the first TEM image or higher than the first TEM image and a half of an area of the rectangular frame is determined as an area of the first grain, an average area of the first grains in the second TEM image is equal to or less than 2000nm² or 1000nm².
The plated article of Claim 4, wherein the average area of second grains in the first TEM image is greater than 5 times or 10 times the average area of first grains in the second TEM image, the respective average areas of the first and second grains are in the same unit of mm².
The plated article of Claim 4 or 5, wherein an area-variance associated with the first grains in the second TEM image is equal to or less than 1/1000 an area-variance associated with the second grains in the first TEM image, and/or
a standard deviation associated with areas of the first grains in the second TEM image is equal to or less than 1/10 a standard deviation associated with areas of the second grains in the first TEM image.
The plated article of any one of Claims 1-6, wherein no flat interface is observed between the first plating layer (81) and the second plating layer (82) in the first TEM image and/or no flat interface is observed between the base member (83) and the first plating layer (81) in the first TEM image.
The plated article of any one of Claims 1-7, wherein a thickness of the first plating layer (81) is less than a thickness of the second plating layer (82).
The plated article of any one of Claims 1-8, wherein a thickness of the first plating layer (81) is equal to or less than 200nm or 150nm.
The plated article of any one of Claims 1-9, wherein a thickness of the second plating layer (82) is in a range between 100nm and 1000nm.
The plated article of any one of Claims 1-10, wherein the first plating layer (81) is formed, in a depth direction directed from a surface of the plated article toward the base member (83), at a side of the base member (83) relative to an intersection point (P1) between a plotting line (PL1) of element ratio of the first metal element of plating layer and a plotting line (PL2) of element ratio of the second metal element of plating layer.
The plated article of Claim 11, wherein a distance between the intersection point (P1) and the first plating layer (81) is equal to or greater than 50nm.
The plated article of any one of Claims 1-12, wherein the first metal element of plating layer is copper, the second metal element of plating layer is tin, and the first plating layer (81) includes speculum alloy.
The plated article of any one of Claims 1-13, wherein a multiplicity of dents are formed on a surface of the second plating layer (82).
The plated article of any one of Claims 1-14, wherein the plated article is a fastener element (4a,4b) attached to a fastener tape (3a,3b), the fastener element (4a,4b) having at least a pair of legs (22,23) and an engagement head (21) to which the pair of legs (22,23) are connected, and the first plating layer (81) formed non-uniformly in separate surfaces of the fastener element (4a,4b).
The plated article of any one of Claims 1-15, wherein the plated article is a fastener element (4a,4b) attached to a fastener tape (3a,3b), the fastener element (4a,4b) including a surface that is at least partially uneven-finished.
A fastener stringer (2a,2b) comprising:
a fastener tape (3a,3b); and

a plurality of fastener elements (4a,4b) attached to a side-edge of the fastener tape (3a,3b) at a predetermined pitch, each fastener element of the plurality of fastener elements (4a,4b) including a base member (83) and a plating layer (84) formed on the base member (83), the base member (83) including at least one base member metal element, wherein

the plating layer (84) includes first and second plating layers (81,82) formed in this order on the base member (83), each of the first and second plating layers (81,82) including at least a first metal element of plating layer that is a same metal element as the base member metal element and a second metal element of plating layer that is a different metal element than the base member metal element;

an element ratio of the first metal element of plating layer continuously decreases as being away from the base member (83) across a total thickness of at least the first and second plating layers (81,82), and an element ratio of the second metal element of plating layer continuously increases as being away from the base member (83) across a total thickness of at least the first and second plating layers (81,82); and

the second plating layer (82) is visually distinguishable from the first plating layer (81) as a layer containing larger grains than grains of the first plating layer (81) in a TEM (Transmission Electron Microscope) image.
The fastener stringer (2a,2b) of Claim 17 wherein the fastener element (4a,4b) has a main surface (51) oriented along a tape surface for defining a thickness of the fastener tape (3a,3b), and
the second plating layer (82), the first plating layer (81), and the base member (83) are formed in this order away from the main surface (51) toward the fastener tape (3a,3b).
The fastener stringer (2a,2b) of Claim 18 wherein the fastener element (4a,4b) includes a pair of legs (22,23) that sandwich the fastener tape (3a,3b),
each leg of the pair of legs (22,23) has a front side (52) connected to a front rim of the main surface (51) and a rear side (53) connected to a rear rim of the main surface (51), and

the second plating layer (82), the first plating layer (81), the base member (83), another first plating layer (81) and another second plating layer (82) are formed in this order between the front side (52) and the rear side (53).