GB2501763A

GB2501763A - Ceramic and metal jewellery

Info

Publication number: GB2501763A
Application number: GB1207875.4A
Authority: GB
Inventors: Brian Berenblut
Original assignee: BJB Ltd
Current assignee: BJB Ltd
Priority date: 2012-05-04
Filing date: 2012-05-04
Publication date: 2013-11-06
Also published as: GB201207875D0

Abstract

An article of jewellery 10 comprising a ceramic body 12 carrying a layer of gold 14 and incorporating a solid gold element, wherein the ceramic body comprises at least one recess for receiving the solid gold element and the gold layer is deposited in a thickness selected so that the surface hardness of the gold layer is dominated by the hardness of the ceramic body. The gold layer may have a thickness at least equivalent to the surface roughness of the ceramic body, but less than 250 nm, preferably less than 100 nm. The gold layer may be deposited on the ceramic layer by sputtering, or may be an ion plated layer. The ceramic body preferably comprises yttrium stabilized zirconia. The solid gold element may comprise two or more ornamental surfaces and may be configured by the user to allow the appearance of the jewellery to be changed.

Description

Ceramic and Metal JeweHery The present invention relates to jewellery and to methods of manufacturing jeweflery, more particularly the invention relates to jewellery comprising layers of precious metals such as gold deposited on a ceramic substrate.

The environmental costs of gold production, both in terms of energy and carbon footprint have been acknowledged and the economic cost can also be very high. Fluctuations in world markets also have an effect. Tn this context there is a desire to reduce the quantity of gold used in items of jewellery so as to reduce their environmental impact and to contr& their retail price.

One well known way to reduce the cost of jewellery and other items is by coating less valuabic mctals with a laycr or plating of gold, and tcchniqucs for gold plating are well known. However, gold plating is susceptible to wear and oflen the plating can be worn away relatively quickly, or scratched to reveal the substrate beneath. Consumers find this unacceptable so there is a need to provide a more durable gold coating.

To address this it is possible to apply a thicker layer of gold so that the ayer takes longer to wear away. However, increasing the thickness of the gold also increases the cost and this is undesirable.

Of course, the aesthetics of jewellery are of paramount importance. From a commercial point of view it is desirable for jewellery to be smooth to within relatively high tolerances. It is also desirable that jewellery should not be easily damaged by impacts, shocks and typical wear and tear.

Thus, the inventors in the present case have recognised a need for robust, visuafly attractive jeweHery and aspects and examples of the invention, as set out in the appended claims, aim to address at least a part of the above described technical problem.

in an aspect there is provides an article ofjewellery comprising a ceramic body cariying a layer of gold and incorporating a solid gold element, wherein the ceramic body comprises at least one recess for receiving the solid gold element and the gold layer is deposited on to the ceramic body in a thickness selected so that the surface hardness of the gold layer is dominated by the hardness of the ceramic body. The inventors in the present case have found that, by appropriate selection of the thickness of the gold layer the hardness of the surface of the gold layer can be substantially equivalent to the hardness of the underlying ceramic (for example the same to within a few percent, e.g. to within 5% or 10%). This has the advantage that the article of jcwellery is highly resistant to scratching and wear and tear.

Preferably the surface hardness of the gold layer being dominated by the hardness of the ceramic body is provided by the gold layer having a thickness at least equivalent to the surface roughness of the ceramic body and less than 250 nanometres. This has the advantage that the surface has a visually attractive finish but, the hardness of the surface is maintained and is substantially harder than gold alone. In some examples the thickness of the layer is less than 200 nanometres, and preferably less than 150 nanometres, or less than 100 nanometres The inventors in the present case have surprisingly found that, when such thin layers are used, the thin film of gold adheres very strongly to the ceramic substrate and provides a durable robust layer which resists peeling or scraping away from the ceramic. Although it is somewhat counterintuitive, it has been found that thicker layers of gold may be more easily peeled back from the substrate.

Typically an article of ceramic will have a degree of surface roughness, which may be characterised by a profile of peaks and valleys across its surface. These deviations from an ideal smooth flat profile (roughness) may be characterised by the maximum height difference between the peaks and valleys on the surface of the ceramic. Tnherently this profile varies across the surface of a piece of ceramic, and varies between different ceramic articles, but for any given piece of ceramic the surface roughness is measurable to an accuracy of nanometres or less using surface metrology techniques that are well known in the art. Preferably the thickness of the gold layer (e.g. at its thickest point) is at least as thick as the maximum height of the surface roughness profile of the ceramic, e.g. the maximum height difference between the peaks and valleys on the surface of the ceramic. The inventors have found that one way to achieve this is by vacuum deposition to grow the gold on to the ceramic, for example a process of physical vapour deposition, PVD, may be used. Usable techniques include: cathodic arc deposition; electron beam PYD; evaporative deposition; pulsed laser deposition; and sputter deposition. Other deposition techniques may also be used. The inventors have found that these approaches are particularly advantageous because the thickness of the gold layer can be closely controlled, the gold adheres strongly to the ceramic substrate and a high quality smooth finish is achieved. For example, by this and other methods it is possible to deposit a gold layer having a thickness of less than 100 microns. The inventors have found that such thin layers are surprisingly robust.

in some cases the gold can be laid down on to the ceramic such that surface hardness of thc gold laycr measured using the Mohs hardncss tcst is at least 7 on the Mohs hardness scale. Typically the hardness of the Zirconium ceramic used in examples of the invention is 8.5 on the Mohs hardness scale. As is known in the art, the Mohs hardness scale is a relative scale in which diamond is assigned a hardness of 10, topaz a hardness of S and so on. The Mohs hardness test is applied by abrading a test material with another material of known hardness to determine which material is harder. The Mohs scale is well known but somewhat arbitrary, but conversions between Mohs hardness and hardness on the Viekers' scale are well known and could be determined by the skilled reader. For example a Mohs hardness of 8.5 is between 1875 and 2000 kg mm2. A Mohs hardness of 7 is between 858 and 1288 kg mni2.

Preferably at least 60%, still more preferably at least 70% of the surface of the ceramic body is covered by the gold layer. Tn some cases the ceramic body is entirely covered by the gold layer. Whilst certainly advantageous, the recess and the solid gold element are both optional features.

An aspect of the invention provides an article of jewellery comprising: a metal link or structural element for coupling the article to another article, or for coupling the article to the human body, and a ceramic body carrying a layer of metal wherein the ceramic comprises an engagement feature for receiving the metal link or structural element to affix the metal link to the ceramic body. Preferably the metal layer comprises a precious metal such as platinum, gold or silver and the metal link or structural element comprises a solid precious metal such as platinum, gold or silver. This and other examples of the invention have the advantage that articles of providing large structures of jewellery having the appearance of being made from precious metal whilst also enabling more intricate or delicate features to be provided than could be provided with a coated ceramic.

in some embodiments the article comprises a recess for receiving a solid metal element and a solid metal element seated in said recess.

in an aspcct there is provided an article ofjewcllery comprising a solid gold elcmcnt and a ceramic body carrying a layer of gold, wherein the ceramic body comprises a recess for recciving the solid gold clement and thc solid gold clement is seated in the recess. This and other examples of the invention have the advantage of providing aesthetically pleasing jewdllery that has the look and feel of gold. Preferably the specific gravity of thc article of jewellery is at least 4 (e.g. 4000 kg m3), still more preferably at least 6 (e.g. 6000 kg m3) at least 8 (e.g. 8000 kg m3).

In some embodiments the article comprises a metal link or structural element to affix the metal link to another article or the human body and the ceramic body comprises an engagement feature for receiving the metal link or structural element Preferably the metal layer comprises a precious metal such as platinum, gold or silver and the metal link or structural element comprises a solid precious metal such as platinum, gold or silver Preferably the gold comprises IS carat gold. In some examples the gold layer comprises 18 canit gold and the metal link or structural element comprise gold of various canits, for example the metal link or structural clement may comprise gold of lower purity than the metal layer. These examples of the invention have the advantage that, for the puiposes fo recycling the metal link or structural element can be mechanically separated from the mechanical body and treated separately whilst the high purity gold can easily be recovered from the ceramic body without contamination.

Preferably the metal link or structural clement comprises a fitting for a chain or an earring fitting. In some examples the metal link or structural element comprises an ear fitting, a bale or bales, chains, or logo tags or other elements. Preferably the ceramic body accounts for the majority of the weight of the article ofjewelleiy. This and other examples of the invention have the advantage of providing physically robust, durable pieces of jewellery without the need to use large quantities of precious metal.

Preferably the metal layer comprises gold and the layer of gold is ion plated on to the ceramic. Preferably the gold layer is 18 carat gold.

Tn some examples the metal link or structural elements comprise gold components (such as fiftings or chains) having a purity selected from the list comprising 9, 10, 14, and 1 carat together with ceramic layered with fine gold.

Preferably the specific gravity of the ceramic in the ceramic body is at least 4.5 (e.g. 4500kg n13), and may be at least 5 (e.g. 5000 kg m3) or at least 5.5 (e.g. 5500 kg m3).

Preferably the specific gravity of the article ofjewcllery is less than 13 (e.g. 13000kg m 3), and may be less than 10 (e.g. 5000 kg m3) or less than (e.g. 5500 kg m3). In some cases the specific gravity is 6 (e.g. 6000 kg nf3). These and other examples of the invention havc the advantage of providing an agreeable weight for relatively bulky articles ofjeweflery, i.e. providing the handling characteristics of gold without excessive weight.

in some examples thc articlc carries an idcntification mark and in somc cases thc idenfification mark is provided on a gold plate or on a solid gold element held in a recess of the ceramic body. This and other examp'es of the invention have the advantage that fine detail or ornamentation can be provided in an inlaid gold item without the need to construct complex features from ceramic.

In some examples the ceramic body comprises a ceramic selected from the list comprising: non-silicate glasses, pure oxide materials (e.g. A1203) and carbides (e.g. SiC). The ceramic material may have a crystalline or a partly crystalline structure, or may be amorphous (e.g. a g'ass). The use of a ceramic body according to the invention has the advantage of being particularly hard and stiff; and in some cases maybe stiffer than steel.

In addition, ceramics may be more heat and corrosion resistant than metals or polymers, andIor may be less dense than some metals and their alloys.

Tn some examples the ceramic body comprises a ceramic selected from the list comprising: oxides of alumina, beryHia and zirconia; non-oxides: carbide, boride, nitride, silicide; and composite materials, such as: particulate-reinforced, fibre-reinforced and combinations of oxides and non-oxides.

In some examples the ceramic body comprises a zirconium dioxide based ceramic.

Tn some examples the ceramic body comprises YSZ. This and other examples have the advantage of providing a hard substrate that is substantially chemically inert. This has the further advantage of providing jewellery that is scratch resistant. The electro-ceramic properties may also be advantageous in processes of manufacture which relate to the electrop'ating of thc ceramic body.

In some examples the ceramic body may be zirconia and/or doped zirconia. Preferably the ceramic is sintered. In some examples at least one organic additive is used to enable the sintering. The sintering may be performed under pressure, as hot pressing, or without additional pressure.

in some examples the ceramic body comprises a polished YSZ ceramic. The metal layer may be sputtered on to the ceramic.

In an aspect there is provided a method of manufacturing an article of jewellery, comprising polishing a ceramic comprising zirconium dioxide ceramics to provide a ceramic body, providing a ceramic fixture in the ceramic body for coupling the ceramic body to a metal structural or ornamental component, polishing an area of the surface of the ceramic body and sputtering a layer of metal on to the polished ceramic body such that the fixture remains accessible to receive said metal structural or ornamental component and coupling a metal structural or ornamental component to the fixture on the ceramic body. Preferably the metal comprises a precious metal such as gold, silver or platinum.

Preferably sputtering comprises a physical vapour deposition (PVD) method, and preferably the layer comprises a thin film.

In sonic examples the ceramic comprises YSZ this has the advantage of being hard and scratch resistant. interestingly, sputtered coatings of gold on YSZ are similarly extremely resistant to scratch and wear-damage and this is of particular advantage in the manufacture ofj ewellery.

Specific embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows an article ofjewellery; and Figure 2 shows a second artic'e ofjeweflery.

Figure I shows an article ofjeweflery 10 comprising a ceramic boy 12 carrying a layer 14 of gold. Thc thickncss of thc laycr of gold is at icast thick cnough to covcr thc surface roughness profile of the ceramic (e.g. to fill the deepest of the microscopic "valleys" on the surfacc of thc ccramic) and is lcss than 100 nanomctrcs thick. The thickncss of the gold is approximately even across the body 12 of the article ofjewellery 10 but there are localised differences to account for the roughness of the surface.

The article of jewellery 10 includes two coupling points 1, iS' which are arranged to rcccivc a structural dcrncnt (not shown in Figure I) in order to couple the artick 10 to another structure. Each coupling 1, 15' comprises a hole through the gold layer 14 and a recess in the ceramic body 12. The recess 19 is 0.4 mm wide and 3 mm deep and is circular in cross section. The cross section of the hole through the gold layer is also circular to enable a rod of circular cross section to be seated in the recess through the hole and form a ncat join with the gold layer.

The coupling points 18, 18' may be arranged to couplc the article to another identical or similar article or to the human body, or to provide a structural component of a larger piece of] ewellery of which the article 10 forms a component.

The ceramic body comprises yttria-stabilized zirconia (YSZ) and is polishcd so that thc maximum deviation in the surface from an ideal smooth profile is less than 1Otrn. Thc gold layer is sputtered on to the ceramic using a process of physical vapour deposition, PYD, as this has been found to provide a particularly smooth, robust and scratch resistant surface.

Other ccramic may also bc uscd, zirconium oxide bascd ccramics arc advantagcous examples and these may include calcia-, magnesia-, ceria-or ahimina-stabilized zirconias, or partially-stabilized zirconias (PSZ). The ceramic need not be zirconium oxide based, any appropriate ceramic will do.

Tn Figure I the reccss 19 is 0.4 miii wide, but it may bc as small as at least 0.1 mm.

Preferably the recess is at least 0.25 mm wide, at least 0.5 mm or at least 0.7mm wide. In some cascs the recess is less than 2mm widc and prcfcrably is less than 1.5mm wide, or may be less than 1mm wide. The recess is preferably circular in cross section but may be of any appropriate cross section and may be tapered and/or may include splines or keyed surfaces arranged to inhibit rotation of a rod of complementary shape seated in the recess.

The recess 19 in Figure 1 is described as being 3mm deep but may be shallower or deeper depending on the requirements of the jewellery. It has been found that recesses of at least 2mm in depth can provide robust fixtures without overly compromise the structural integrity of the ceramic body and which enable The recess and/or the hole through the gold layer may be threaded or comprise other engagement features, such as non return fittings to enable structural elements to be robustly held in the recess without the need for adhesives.

Figure 2 shows an article of jewellery 40 comprising a ceramic body 42 covered with a layer of gold 44. The ceramic body 40 comprises a recess 46 for receiving a solid gold element 48.

The gold layer 44 covers the ceramic 42 in the recess 46 so that when the solid gold element 48 is not held in the recess the appearance of the article of jewellery remains unspoilt. The solid gold element 48 is configured to be retained in the recess 46 so as to be selectively detachable from the article. The solid gold element 48 includes an ornamental surface 50 configured to face outward from the recess. The remaining features of the embodiment described in relation to Figure 2 are substantially as described in relation to the embodiment of Figure 1.

it is contemplated that the feature of the coupling 18, 18' may be used in conjunction with the embodiment of Figure 2. Likewise it is contemplated that the feature of the recess and solid gold element 42 may be used in conjunction with the embodiment of Figure I. Other combinations of features will be apparent to the skilled practitioner in the context of the

present disclosure.

The solid gold clement 48 may have two or more ornamental surfaces and may be reversib'e so as to enable the appearance of the jewellery to be changed by the user. The recess 46 is shown as being circularly symmetric and this may be advantageous where there is a wish to enable the orientation of the solid gold element 48 to be modified by a user of the jewellery (such as a retailer at the point of sale) or by the owner/wearer of the jewellery. The solid gold element 48 may also be circularly symmetric for similar reasons.

In some cases the solid gold element may be comprise a surface feature configured to engage with the recess such that the solid gold element can only be fitted in to the recess in one of a selected plurality of orientations, in some cases the surface feature may be configured so that only one orientation is possible. This and other examples of the invention have the advantage of enabling jewellery pieces to be modified and/or assembled by untrained personnel without compromising the aesthetic quality and/or symmetry of the end product.

The gold layer (14 in Figure 1,44, in Figure 2) may cover all of the ceramic body or may only partially cover it. In some cases a region of ceramic may be exposed and ornamentation such as gems may be seated in the ceramic. This has the advantage that a robust setting for genis can be provided by the ceramic. In sonic cases the ceraniic may simply be exposed to provide a visual feature of the jewellery and this may be of particular advantage where heavy wear or abrasion of surfaces is to be expected. One case in which this has been found to be of use is in the provision of surfaces for pendants that are typically worn under clothing in day to day use.

Where the article ofjewellery includes a recess for receiving a solid gold element such as element 48 the gold layer may not fully cover the recess, this has the advantage that the ceramic may comprise an engagement feature such as threading or a non return fitting such as a push or clip fitting. It has been found that manufacturing these engagement features out of ceramic provides a particularly robust engagement between the solid gold element and the ceramic body. In some cases the gold may actually cover the recess and in these cases the gold layer itself may provide the engagement feature, for example a thread may be etched into or fornied from the gold layer.

Tn sonic examples the solid gold element may comprise a ferrous component and the ceramic body may comprise a magnet disposed adjacent the recess 46 and configured to retain the solid gold element in the recess.

The ceramics used for the embodiment of Figure 2 are typically substantially as described above with reference to Figure 1. The solid cold element need not comprise gold and may comprise other materials for example silver or platinum or other metals may be used, in some cases the element 4 is non metal.

Other combinations and variations of features will be apparent to the skilled reader in the

contcxt of thc prcscnt disclosure.

Claims

Claims: An article of jewellery comprising a ceramic body carrying a layer of gold and incorporating a solid gold element, wherein the ceramic body comprises at least one recess for receiving thc solid gold dement and the gold layer is deposited on to the ceramic body in a thickness selected so that the surface hardness of the gold layer is dominated by the hardness of the ceramic body.
2. The article ofjewellery of claim I wherein the surface hardness of the gold layer being dominated by the hardness of the ceramic body comprises the gold layer having a thickness at least equivalent to the surface roughness of the ceramic body and less than 250 nanometres.
3. The article of jcwellery of claim 2 wherein the surface roughness of the ceramic body comprises the maximum height of the roughness profile.
4. The article of jewellery of claim 2 or 3 wherein the thickness of the gold layer is less than 1 00 nanometres.
5. The article of jewefleiy of any preceding daim wherein the gold sayer is deposited or grown on the ceramic by sputtering.
6. The article of jewellery of any preceding claim in which the surface hardness of the gold layer measured using the Mohs hardness test is at least 7 on the Mohs hardness scale.
7. An article of jewellery according to any preceding claim wherein the solid gold element is operable to be seated in the recess so as to inhibit removal of the solid gold element from the recess.
8. The article of daim 7 in which the solid gold element comprises a structural element adapted to affix the article to another article, or to the human body.
9. The article of claim 7 or 8 in which the recess comprises an engagement feature for cooperating with the solid gold element so as to inhibit removal of the solid gold element from the recess.
10. The article of claim 8 or 9 in which the structural clement comprises at least one of: a fitting for a chain or an earring fitting, a bale or bales, chains, or logo tags or other elements.
II. The article of any preceding claim in which the ceramic body accounts for the majority of the weight of the article ofjewellery.
12. The article of any preceding claim in which the layer of gold comprises an ion plated layer.
13. The article of any preceding claim in which the solid gold element comprises gold having a purity selected from the list comprising 9, tO, 14, and IS carat.
14. The article of any preceding claim in which the average density of the article of jewellery is at least 5000 kg m3.
15. The article of any preceding claim in which the article carries an identification mark provided on the solid gold element.
16. The article of any preceding claim in which the ceramic body comprises a ceramic selected from the list comprising: non-silicate glasses, pure oxide materials (e.g. A1203) and carbides (e.g. SiC).
17. The article of any preceding claim comprising a layer of titanium nitride between the ceramic body and the gold layer.
18. The article of any preceding claim in which the ceramic body comprises a ceramic selected from the list comprising: oxides of alumina, beryllia and zirconia; non- oxides: carbide, boride, nitride, silicide; and composite materials, such as: particulate-reinforced, fibre-reinforced and combinations of oxides and non-oxides.
19. The article of any preceding claim in which the ceramic body comprises a zirconium dioxide based ceramic.
20. The article of any preceding claim in which the ceramic body comprises yttrium stabilised zirconia.
21. The article of any preceding claim in which the solid gold element comprises at least one ornamental face and an engagement face configured to engage with a feature of the ceramic body recess such that the solid gold element can only be fitted in to the recess in one of a selected plurality of orientations.
22. The article of any preceding claim in which the solid gold element comprises two or more ornamental surfaces and is configured to be oriented by a user so as to enable the appearance of the jewellery to be changed.
23. A method of manufacturing an article ofjewellery, comprising: polishing a ceramic comprising zirconium dioxide ceramics to provide a ceramic body, providing a ceramic fixture in the ceramic body for coupling the ceramic body to a metal structural or ornamental component, polishing an area of the surface of the ceramic body and applying a layer of metal on to the polished ceramic such that the thicki ess of the surface layer is comparable with the surface roughness of the polished ceramic, and the fixture remains accessible to receive said metal structural or ornamental component; and coupling a metal structural or ornamental component to the fixture on the ceramic body.
24. The method of claim 23 in which the metal comprises a precious metal such as gold, silver or platinum.
25. The method of claim 23 or 24 in which applying the layer comprises physical vapour deposition (PVD) or sputtering.
26 The method of daim 23, 24, or 25 in which being comparable with the surface roughness comprises being at least as thick as the maximum height of the roughness profUe of the ceramic.
27. The method of any of claims 23 to 26 in which the layer is less than 250 nanometres in thickness.
2S. The method of any of claims 23 to 27 further comprising depositing a layer of titanium nitride on to the ceramic prior to applying the layer.
29. An article of jewellery substantially as described herein with reference to the accompanying drawings.