Interference pigment comprising metal core selected from group consisting of AU, AG, PD, RH, RU, PT, OS, IR and alloys thereof

Abstract

The invention relates to a multilayer interference pigment (1) comprising in succession: a metal core (2) in the form of flakes, said metal core (2) comprising a material selected from the group consisting of gold, silver, palladium, rhodium, ruthenium, platinum, osmium, iridium and alloys thereof; a first layer (3) of transparent dielectric material; and a second discontinuous metal layer (4).

Description

[0001] This application is a divisional application of a patent application with application number 201880014229.7, application date February 26, 2018, and invention name “Interference pigments comprising a metal core selected from AU, AG, PD, RH, RU, PT, OS, IR and alloys thereof”. Technical Field

[0002] The present invention relates to a novel interference pigment, which is particularly applicable to the fields of watches, jewellery and cosmetics. Technical Background

[0003] The color palette produced by the interference of reflected light on a multilayer structure is well known. Reference may be made to documents EP 0 905 205 and US 6 626 989 which disclose pearlescent pigments comprising a mica core coated with a titanium oxide layer.

[0004] Recently, interference pigments with a metal core have become more popular. The choice of core metal is mainly limited to aluminum. Although this type of pigment already has an attractive aesthetic appearance, the intensity and brightness of the interference color can be further improved by exploiting the optical properties of the core metal. SUMMARY OF THE INVENTION

[0006] The present invention thus provides novel interference pigments which can improve the aesthetic appearance of articles comprising them.

[0007] To this end, pigments, their use and preparations are proposed according to the appended claims.

[0008] More precisely, the invention proposes a multilayer interference pigment which comprises successively:

[0009] - a metal core in the form of a thin sheet, the metal core comprising a material selected from the group consisting of gold, silver, palladium, rhodium, ruthenium, platinum, osmium, iridium and alloys thereof;

[0010] - a first layer of transparent dielectric material;

[0011] - A second discontinuous metal layer.

[0012] By means of this metal core, which is made of a noble metal and has an increased reflectivity in at least a part of the visible spectrum (preferably greater than that of aluminum), the interference colors are increased in brightness and intensity compared to those obtained with conventional interference pigments. This results in coatings or solid articles with a specific sparkle, which are highly valued in the fields of horology, jewelry and cosmetics.

[0013] According to a specific embodiment of the present invention, the interference pigment has one or a suitable combination of the following characteristics:

[0014] - the metal core is made of a material selected from the group consisting of gold, silver, rhodium and alloys thereof, more preferably selected from the group consisting of gold, silver and alloys thereof;

[0015] - it comprises a third protective layer formed of a transparent dielectric material or a transparent resin;

[0016] - the dielectric material of the first and third layers is selected from TiO2, SiO2, Al2O3, MgF2, AlN, Ta2O5, Si3N4 ZnS, ZnO, ZrO2, Cr2O3, CeO2, Y2O3, HfN, HfC, HfO2, La2O3, MgO, Sb2O3, SiO, Se2O3, SnO2 and WO3;

[0017] - the second metal layer is made of a material selected from the group consisting of silver, gold, aluminum, titanium, palladium, platinum, ruthenium, osmium, iridium, tin, chromium, iron, cobalt, nickel, copper, zinc, rhodium and alloys thereof;

[0018] - the metal core has an average transverse diameter of 2-300 μm, preferably 5-100 μm, more preferably 10-30 μm, and an average thickness of 20-1000 nm, preferably 300-500 nm;

[0019] - the first layer has a thickness of 50-500 nm, preferably 300-400 nm;

[0020] - the second layer and the third layer have a thickness of 1-30 nm, preferably 1-10 nm;

[0021] - The second layer is in the form of spaced particles.

[0022] The invention also relates to an article, in particular a decorative piece for a timepiece or jewellery comprising an interference pigment as described above.

[0023] According to a particular embodiment of the invention, the article has a coating comprising interference pigments or has interference pigments within its mass.

[0024] The invention also relates to a watch or an article of jewellery comprising an article with interference pigments.

[0025] The invention also relates to the use of the interference pigment in paint, ink or cosmetic formulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention will now be described in more detail with reference to the accompanying drawings, which are given by way of example and not limitation, in which:

[0028] Figure 1 Schematic representation of the different layers of the interference pigments according to the invention,

[0029] Figure 2The optical path of light through the interference pigments according to the invention is schematically represented.

[0030] Detailed description of the invention

[0031] The present invention relates to a multilayer interference pigment, which comprises a core made of pure or alloyed precious metals such as gold, silver, platinum, palladium, ruthenium, rhodium, osmium or iridium. The reflectivity of these metals in all or part of the visible spectrum (380nm-780nm) is greater than 70%, even greater than 80% or even 90%. The selected metal is preferably rhodium, gold, silver or its alloy, more preferably gold, silver or its alloy. For wavelengths greater than 550nm, gold has an increased reflectivity. Therefore, it is preferred when warm colors (red, yellow) are needed. However, silver has an increased reflectivity in the wider range of the visible spectrum, which also makes it possible to obtain blue and green. In the case of alloys, for example Ag-Pt alloys are selected.

[0032] Figure 1 The pigment 1 according to the invention shown in FIG. 1 comprises a metal core 2 coated with a first layer 3 of a dielectric material, which forms an interference medium, which itself is covered by a second layer 4 of a metallic material and can be coated by a third protective layer 5 .

[0033] The metal core 2 is in the form of an elongated thin sheet, with an average transverse diameter D of 2-300 μm, preferably 5-100 μm, more preferably 10-30 μm. Its average thickness E is 20-1000 nm, preferably 300-500 nm. Generally, the shape factor of the thin sheet, that is, the ratio of the average transverse diameter to the average thickness, is 5-1000, preferably 10-500.

[0034] The first layer 3 comprises a transparent dielectric material, which can be composed of, for example, TiO2, SiO2, Al2O3, MgF2, AlN, Ta2O5, Si3N4, ZnS, ZnO, ZrO2, Cr2O3, CeO2, Y2O3, HfN, HfC, HfO2, La2O3, MgO, Sb2O3, SiO, Se2O3, SnO2, or WO3, preferably SiO2. The thickness of this layer is 50-500nm, preferably 300-400nm, and the thickness and refractive index of the dielectric material are selected according to the desired interference color.

[0035] The second layer 4 is formed by a metal or a metal alloy and is designed to reflect light on the surface of the interference pigment. The metal is preferably selected from silver, gold, aluminum, titanium, palladium, platinum, ruthenium, rhodium, osmium, iridium, tin, chromium, iron, cobalt, nickel, copper, zinc, rhodium and its alloy. More preferably selected from silver, gold, aluminum, rhodium and its alloy. The thickness of this layer is 1-30nm, preferably 1-10nm. This layer is configured to be able to transmit a portion of the light beam incident on the metal core. Therefore, it is preferably discontinuous, uneven and can be formed by particles. In the latter case, the particles are preferably arranged at intervals, and the intervals between the particles are several nanometers. Of course, such a second discontinuous metal layer makes it possible to reflect a portion of the light beam and transmit another part of the light beam to the metal core.

[0036] The optional third protective layer 5 is designed to protect the second metal layer from oxidation or wear. The layer is preferably made of a transparent dielectric material, such as TiO2, SiO2, Al2O3, MgF2, AlN, Ta2O5, du Si3N4, ZnS, ZnO, ZrO2, Cr2O3, CeO2, Y2O3, HfN, HfC, HfO2, La2O3, MgO, Sb2O3, SiO, Se2O3, SnO2, WO3 or a transparent resin. The thickness of the layer is 1-30 nm, preferably 1-10 nm.

[0037] The invention does not exclude the insertion of an intermediate layer between the metal core and the first layer and / or between the first and second layer in order to increase the adhesion between the different composition layers of the interference pigment.

[0038] like Figure 2 As shown, part of the incident light is reflected at the outer metal layer 4, while another part is transmitted and reflected at the metal core 2. Due to the effects of interference (which differs slightly depending on the viewing angle), the difference in the trajectory of the reflected light beams produces color.

[0039] According to the invention, the metal core can be made of leaf, for example gold or silver leaf, the outer layer being deposited by CVD, PVD, electrochemically or by non-electrolytic methods, and the whole being subsequently crushed. The multilayer pigment can also be made of flakes obtained chemically by wet or dry processes, or even by atomization, which can be crushed before coating.

[0040] The pigment powder thus obtained can be dispersed in a suitable medium depending on the application. Thus, it can be used in coatings, inks, cosmetic formulations and generally in coating formulations.

[0041] Pigment powders can also be used as they are. In this configuration, previously deposited powders are compacted onto a substrate and then sintered in a uniform or selective manner by the action of locally applied heat (e.g. by laser). This results in a dense coating covering all or part of the substrate. Solid articles can also be formed by compacting and thickening pigment powders. Solid particles can also be produced by additive manufacturing.

[0042] For example, in the watch sector, the pigments can be used after being dispersed in a suitable medium, or used as such to coat or decorate decorative parts (dials, bezels, case bands, bases, clasps...) or to form solid decorative parts (dials, hands, pointers, buttons, etc.).

[0043] Finally, it should be noted that the pigment with a core made of pure gold and its different layers can be titrated to 18 carats. The pigment thus successively contains:

[0044] - Gold core, 400nm thick, 30μm lateral diameter,

[0045] - first SiO2 coating, thickness 330nm,

[0046] - Second Ag metal coating, thickness 5nm,

[0047] - The third SiO2 protective layer has a thickness of 10nm,

[0048] The gold content is 79.01% by weight, which is 75% greater than the required 18-karat gold content.

[0049] The metal core can also be made of other precious metal alloys to meet legal standards, such as Pd500 or Pt900.

[0050] Reference numeral index

[0051] (1) Interference pigments

[0052] (2) Metalcore

[0053] (3) The first layer, also called the dielectric layer

[0054] (4) The second layer, also called the metal layer

[0055] (5) The third layer, also called the protective layer

[0056] D: Transverse diameter of the metal core forming the flake

[0057] E: Thickness of the metal core forming the flake.

Claims

1. The multilayer interference pigment (1) comprises successively: - a metal core (2) in the form of a flake, the metal core (2) comprising a material selected from the group consisting of gold, silver, palladium, rhodium, ruthenium, platinum, osmium, iridium and alloys thereof; - a first layer (3) of a transparent dielectric material; The second discontinuous metal layer (4) makes it possible both to reflect a part of the light beam and to transmit another part of this light beam to the metal core.

2. The pigment according to claim 1, wherein the metal core (2) comprises a material selected from the group consisting of gold, silver, rhodium and alloys thereof, more preferably a material selected from the group consisting of gold, silver and alloys thereof.

3. The pigment according to claim 1 or 2, comprising a third protective layer (5) formed of a transparent dielectric material or a transparent resin.

4. The pigment according to any one of the preceding claims, wherein the dielectric material of the first layer (3) and the third layer (5) is selected from TiO2, SiO2, Al2O3, MgF2, AlN, Ta2O5, Si3N4 ZnS, ZnO, ZrO2, Cr2O3, CeO2, Y2O3, HfN, HfC, HfO2, La2O3, MgO, Sb2O3, SiO, Se2O3, SnO2 and WO3.

5. The pigment according to any one of the preceding claims, wherein the second metal layer (4) comprises a material selected from the group consisting of silver, gold, aluminum, titanium, palladium, platinum, ruthenium, rhodium, osmium, iridium, tin, chromium, iron, cobalt, nickel, copper, zinc, rhodium and alloys thereof.

6. The pigment according to any one of the preceding claims, wherein the metal core (2) has an average transverse diameter of 2-300 μm, preferably 5-100 μm, more preferably 10-30 μm, and an average thickness of 20-1000 nm, preferably 300-500 nm.

7. The pigment according to any of the preceding claims, wherein the first layer (3) has a thickness of 50-500 nm, preferably 300-400 nm.

8. The pigment according to any one of the preceding claims, wherein the second layer (4) and the third layer (5) have a thickness of 1 to 30 nm, preferably 1 to 10 nm.

9. The pigment according to any one of the preceding claims, wherein the second layer (4) is in the form of spaced-apart particles.

10. Articles and decorative parts, in particular for timepieces or jewellery, comprising an interference pigment according to any one of the preceding claims.

11. The article according to claim 10, having a coating comprising interference pigments.

12. The article of claim 10, comprising interference pigments in its mass.

13. A watch or piece of jewellery comprising an article according to any one of claims 10 to 12.

14. Use of the interference pigment (1) according to any one of claims 1 to 9 in coatings, inks or cosmetic formulations.

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