Timepiece or piece of jewellery made of gold

Abstract

A timepiece or piece of jewellery made of a nickel free and cobalt free gold alloy, the composition of which includes by weight between 75% and 77.5% gold, between 1.2 and 1.6% palladium, and between 20.1 and 23.8% copper.

Claims

1. A timepiece or piece of jewellery manufactured in a nickel free and cobalt free gold alloy, a weight percent composition of which comprises: between 75% and 77.5% gold, between 1.35 and 1.45% palladium, between 20.1 and 23.8% copper, and the nickel free and cobalt free gold alloy further comprises iridium, wherein the nickel free and cobalt free gold alloy includes a resistance to a discoloration that yellows a color of the nickel free and cobalt free gold alloy when the nickel free and cobalt free gold alloy is exposed in at least one of a saline atmosphere, an acid atmosphere, and an atmosphere of sweat, and the resistance to the discoloration of the nickel free and cobalt free gold alloy is greater than that of a 5N red gold alloy according to ISO standard 8654.

2. The timepiece or piece of jewellery according to claim 1, wherein the alloy comprises between 0.45 and 2% by weight of an element selected from among iron, zinc, silver, and indium, or a combination of the elements.

3. The timepiece or piece of jewellery according to claim 2, wherein the alloy comprises 0.48% platinum.

4. The timepiece or piece of jewellery according to claim 3, wherein the alloy comprises 1.81% silver.

5. The timepiece or piece of jewellery according claim 1, wherein the alloy comprises by weight at most 1% of any one element or of a combination of elements chosen from among gallium, magnesium, calcium, lithium, aluminium, sodium, titanium, molybdenum, tin, silicon, rhodium, zirconium, potassium, and chromium.

6. The timepiece or piece of jewellery according to claim 1, wherein the alloy includes a maximum of 0.05% by weight of an element chosen from among iridium, rhenium, ruthenium.

7. The timepiece or piece of jewellery according to claim 6, wherein the alloy comprises 0.01% by weight iridium.

8. The timepiece or piece of jewellery according to claim 1, wherein the alloy comprises 1.4% by weight palladium.

9. The timepiece or piece of jewellery according to claim 1, wherein the resistance to the discoloration of the nickel free and cobalt free gold alloy is greater than that of a gold alloy comprising 75% gold, 20.5% copper, and 4.5% silver by weight, or that of a gold alloy comprising 76.5% gold, 21% copper, and 2.5% platinum by weight.

10. An 18 carat red gold based alloy, formed of a mixture comprising by weight: between 75% and 77.5% gold, 1.35 and 1.45% palladium, 20.1% to 23.8% copper, and the mixture further comprises iridium and does not include nickel or cobalt, wherein the mixture includes a resistance to a discoloration that yellows a color of the mixture when the mixture is exposed in at least one of a saline atmosphere, an acid atmosphere, and an atmosphere of sweat, and the resistance to the discoloration of the mixture is greater than that of a 5N red gold alloy according to ISO standard 8654.

11. The gold based alloy according to claim 10, wherein the alloy comprises between 0.5% and 2.0% by weight of an element selected from among the group including iron, zinc, silver, and indium, or a combination thereof.

12. The gold based alloy according to claim 11, wherein the alloy includes 0.48% by weight platinum.

13. The gold based alloy according to claim 12, wherein the alloy includes 1.81% by weight silver.

14. The gold based alloy according to claim 10, wherein the alloy includes a maximum of 1.0% by weight of any of elements selected from the group including gallium, magnesium, calcium, lithium, aluminium, sodium, titanium, molybdenum, tin, silicon, rhodium, zirconium, potassium, and chromium.

15. The gold based alloy according to claim 10, wherein the alloy comprises a maximum of 0.5% by weight of any one element or a combination of elements selected from among the group including iridium, rhenium, and ruthenium.

16. The gold based alloy according to claim 15, wherein the alloy includes 0.01% by weight iridium.

17. An 18 carat red gold based alloy, formed of a mixture comprising by weight: between 75% and 77.5% gold, 1.35 and 1.45% palladium, 20.1% to 23.8% copper, and the mixture further comprises platinum and does not include nickel or cobalt, wherein the mixture includes a resistance to a discoloration that yellows a color of the mixture when the mixture is exposed in at least one of a saline atmosphere, an acid atmosphere, and an atmosphere of sweat, and the resistance to the discoloration of the mixture is greater than that of a 5N red gold alloy according to ISO standard 8654.

18. A timepiece or piece of jewellery manufactured in a nickel free and cobalt free gold alloy, a weight percent composition of which comprises: between 75% and 77.5% gold, between 1.35 and 1.45% palladium, between 20.1 and 23.8% copper, and the nickel free and cobalt free gold alloy further comprises an element chosen from among iridium, rhenium, and ruthenium, wherein the nickel free and cobalt free gold alloy includes a resistance to a discoloration that yellows a color of the nickel free and cobalt free gold alloy when the nickel free and cobalt free gold alloy is exposed in at least one of a saline atmosphere, an acid atmosphere, and an atmosphere of sweat, and the resistance to the discoloration of the nickel free and cobalt free gold alloy is greater than that of a 5N red gold alloy according to ISO standard 8654.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the invention will appear upon reading the following detailed description, with reference to the annexed drawings, in which:

(2) FIG. 1 shows the change in colour E for alloys N126, N128, N129 an N139 and two prior art 18 carat red gold alloys, namely alloys N113 and N103, with time in a saturated NaCl solution test at 70 C.

(3) FIG. 2 shows the change in colour E for alloys N126, N128, N129 and N139 and two prior art 18 carat red gold alloys, namely alloys N113 and N103, with time in an artificial sweat test at 40 C.

(4) FIG. 3 shows the change in colour E for alloys N126, N128, N129 and N139 and two prior art 18 carat red gold alloys, namely alloys N113 and N103, with time in an acid rain test at 70 C.

(5) Table 1 shows example alloy compositions in weight % o according to the invention with the exception of alloys N103 and N113 which respectively represent prior art 18 carat red gold alloy compositions.

(6) TABLE-US-00001 TABLE 1 N.sup.o Au. Pd. Cu. Pt. Ag. Ir. 126 773.9 14.0 212.0 0.1 128 769.1 14.0 212.0 4.8 0.1 129 751.0 14.0 212.0 4.8 18.1 0.1 139 751.0 14.0 216.8 18.1 0.1 103 750.7 204.3 45 113 765 210 25
Each of these gold alloys was subjected to three discolouration tests, respectively in a saturated sodium chloride solution, in an artificial sweat solution and in an acid rain solution. The discolouration of each alloy was then measured. Table 2 sets out the composition of the test solutions and the thermal conditions in which they were used. The artificial sweat and acid rain test compositions represent the conditions that a timepiece may experience during wear in the climatic conditions of areas of Asia.

(7) TABLE-US-00002 TABLE 2 Temperature Test [ C.] Formula Saturated 70 Deionized Water dl NaCl NaCl to saturation (at 70 C.) Artificial 40 Citizen type acid sweat sweat Deionized Water dl Sodium chloride: 9.9 g/l Sodium sulphide: 0.8 g/l Urea: 1.7 g/l Lactic acid: 1.4 ml/l Sucrose: 0.2 g/l Ammonia solution NH.sub.3H.sub.20: 0.22 ml/l Hydrochloric acid: quantity necessary to bring the pH to 3.6 (at 25 C.) Acid rain 70 Composition Hangzou (pH = 4.5): Deionized Water dl NaF: 5.8 mol/l. MgCl.sub.2: 7.1 mol/l CaSO.sub.4: 52 mol/l KNO.sub.3 5 mol/l HNO.sub.3: 31.4 mol/l (NH.sub.4)SO.sub.4: 40 mol/l Na.sub.2SO.sub.4: 18 mol/l
The three discolouration tests were performed on gold alloy washers having a diameter of 20 mm and a thickness of 2.5 mm. The washers were polished in succession with 320, 600, 1200, 2400 grit sandpaper up to felt containing diamond particles of 3 to 1 m mean diameter.

(8) Each washer was immersed in 200 ml of a solution corresponding to the tests set out in Table 2 for 42 days. Each washer was placed at the bottom of a closed vial (65 mm, made of polypropylene). For statistical reasons, 3 washers of each alloy from Table 1 were tested for each of the three tests.

(9) The washers were removed and rinsed to measure discolouration at different times during the test period and to observe the evolution of discolouration. It was then possible to draw the curves of FIGS. 1 to 3.

(10) The change in colour or discolouration Ei after i days was calculated in accordance with the following formula:
E.sub.i={square root over ((L.sub.i*L.sub.0*).sup.2+(a.sub.i*a.sub.0*).sup.2+(b.sub.i*b.sub.0*).sup.2)}.
where L*, a*, b* are colorimetric values of samples measured with a Varian Cary 1E spectrophotometer with an integrating sphere of 70 mm.

(11) The results of the discolouration test in saturated NaCl solution at 70 C. show that the red gold alloys according to the invention, alloys N126, N128, N129 and N139, discolour considerably more slowly than the prior art 18 carat red gold alloy N103 in this saline atmosphere. These results are illustrated in FIG. 1, which shows that the variation in E between prior art alloy N103 and alloy N129 according to the invention evolves from 1.5 after 2 days to virtually 3 after a period of 42 days.

(12) The results of the discolouration test in the artificial sweat solution at 40 C. show that the red gold alloys according to the invention, alloys No 126, N128, N129 and N139, discolour considerably more slowly than the prior art 18 carat red gold alloy N103 in this atmosphere of sweat. These results are illustrated in FIG. 2, which shows that the variation in E between prior art alloy N103 and alloy N129 according to the invention evolves from 0.4 after 2 days to virtually 0.8 after a period of 42 days.

(13) The results of the discolouration test in the acid rain solution at 70 C. show that the red gold alloys according to the invention, alloys N126, N128, N129 and N139, discolour considerably more slowly than the prior art 18 carat red gold alloy N103 in this acid atmosphere. These results are illustrated in FIG. 3, which shows that the variation in E between prior art alloy N103 and alloy N129 according to the invention evolves from 0.5 after 5 days to virtually 2 after a period of 42 days.

(14) These tests therefore clearly show that the resistance to discolouration of the alloys according to the invention is considerably improved compared to the prior art 18 carat gold alloys in saline and acid atmospheres and slightly improved in the case of the artificial sweat test.