CH713536B1 - Interferential pigment. - Google Patents

Abstract

The present invention relates to a multilayer interference pigment (1) comprising successively: a metallic core (2) in the form of a flake, the metallic core (2) comprising a material chosen from among gold, silver, palladium , rhodium, ruthenium, platinum, osmium, iridium and one of their alloys; a first layer (3) of a transparent dielectric material; a second metallic layer (4).

Description

Technical area

The present invention relates to a new interference pigment with a more particular field of application in the fields of watchmaking, jewelry and cosmetics.

Technological background

The creation of a color palette by interference of the light reflected on multilayer structures is well known. Mention may be made, for example, of documents EP 0 905 205 and US 6 626 989 which disclose pearl pigments comprising a mica core coated with a layer of titanium oxide.

More recently, interference pigments with a metallic core have become widespread. The choice of core metal was mainly limited to aluminum. Although this type of pigment already has an attractive aesthetic appearance, the intensity and the brilliance of the interference colors can be further improved by, among other things, playing on the optical properties of the core metal.

Summary of the invention

[0004] The present invention thus proposes a new interference pigment which makes it possible to improve the aesthetic appearance of the part comprising it.

[0005] To this end, a pigment, its use and a part according to the appended claims are proposed.

More specifically, the present invention provides a multilayer interference pigment comprising successively: a metallic core in the form of a flake, the metallic core comprising a material chosen from gold, silver, palladium, rhodium, ruthenium, platinum, osmium, iridium and one of their alloys ; a first layer of a transparent dielectric material; a second metallic layer.

[0007] Thanks to this metallic heart made of a precious metal exhibiting a high level of reflectance, and preferably greater than that of aluminum, in at least part of the visible spectrum, the interference colors gain in brightness and intensity compared to those obtained with a conventional interference pigment. This results in coated or solid parts exhibiting a particular shine appreciated in the field of watchmaking, jewelry and cosmetics.

[0008] According to particular embodiments of the invention, the interference pigment exhibits one or an appropriate combination of the following characteristics: the metallic core comprises a material chosen from gold, silver, rhodium and one of their alloys and, more preferably, chosen from gold, silver and one of their alloys; it comprises a third protective layer formed of a transparent dielectric material or of a transparent resin; the dielectric material of the first layer and of the third layer is chosen from TiO2, SiO2, Al2O3, MgF2, AlN, Ta2O5, Si3N4ZnS, ZnO, ZrO2, Cr2O3, CeO2, Y2O3, HfN, HfC, HfO2, La2O3, MgO, Sb2O3, SiO, Se2O3, SnO2 and WO3; the second metallic layer comprises a material chosen from among silver, gold, aluminum, titanium, palladium, platinum, ruthenium, osmium, iridium, tin, chromium, iron , cobalt, nickel, copper, zinc, rhodium and one of their alloys; the metal core has an average transverse diameter of between 2 and 300 µm, preferably between 5 and 100 µm and more preferably between 10 and 30 µm, and an average thickness of between 20 and 1000 nm and, preferably, between 300 and 500 nm ; the first layer has a thickness between 50 and 500 nm and, preferably, between 300 and 400 nm; the second layer and the third layer have a thickness between 1 and 30 nm and, preferably, between 1 and 10 nm; the second layer is discontinuous; the second layer is in the form of particles arranged at intervals.

[0009] The present invention also relates to a part and, in particular to a trim part, for watchmaking or jewelry comprising interference pigments as described above.

According to particular embodiments of the invention, the part comprises a coating comprising interference pigments or comprises bulk interference pigments.

The present invention also relates to the watch or to the jewel comprising the part with the interference pigments.

[0012] It also relates to the use of the interference pigments described above in formulations of paints, inks or cosmetics.

Brief description of the figures

The invention will be described below in more detail with the aid of the accompanying drawings, given by way of non-limiting examples, in which: FIG. 1 schematically represents the different layers of the interference pigment according to the invention . FIG. 2 schematically represents the optical paths of light through the interference pigment according to the invention.

Detailed description of the invention

The present invention relates to a multilayer interference pigment comprising a core made of a pure or alloyed precious metal such as gold, silver, platinum, palladium, ruthenium, rhodium, osmium or iridium. These metals have a reflectance level greater than 70%, or even greater than 80 or even more than 90% in all or part of the visible spectrum (380 nm - 780 nm). The metals chosen are preferably rhodium, gold, silver or one of their alloys and, more preferably, gold, silver or one of their alloys. Gold exhibits high reflectance for wavelengths greater than 550 nm. It is therefore preferred when warm colors (red, yellow) are desired. Silver, on the other hand, exhibits high reflectance over a wider range of the visible spectrum, which also results in bluish and green colors. In the case of an alloy, the choice is, for example, an Ag-Pt alloy.

The pigment 1 according to the invention shown in Figure 1 comprises the metal core 2 coated with a first layer 3 of a dielectric material which forms the interference medium, itself coated with a second layer 4 of a metallic material, optionally coated with a third protective layer 5.

The metal core 2 is in the form of an elongated flake having an average transverse diameter D of between 2 and 300 μm, preferably between 5 and 100 μm and more preferably between 10 and 30 μm. It has an average thickness E of between 20 and 1000 nm and, preferably, between 300 and 500 nm. In general, the form factor of the sequins, i.e. the ratio of the average transverse diameter to the average thickness is between 5 and 1000 and, preferably, between 10 and 500.

The first layer 3 comprises a transparent dielectric material which may, for example, be TiO2, SiO2, Al2O3, MgF2, AlN, Ta2O5, Si3N4, ZnS, ZnO, ZrO2, Cr2O3, CeO2, Y2O3, HfN, HfC, HfO2 , La2O3, MgO, Sb2O3, SiO, Se2O3, SnO2, or WO3, with a preference for SiO2. This layer has a thickness between 50 and 500 nm and, preferably, between 300 and 400 nm, the thickness and the refractive index of the dielectric material being selected as a function of the desired interference color.

The second layer 4 is formed of a metal or a metal alloy intended to reflect the light on the surface of the interference pigment. The metal is preferably chosen from silver, gold, aluminum, titanium, palladium, platinum, ruthenium, rhodium, osmium, iridium, tin, chromium, iron , cobalt, nickel, copper, zinc, rhodium and one of their alloys. It is more preferably chosen from among silver, gold, aluminum, rhodium and one of their alloys. This layer has a thickness between 1 and 30 nm and, preferably, between 1 and 10 nm. The layer is configured to allow the transmission of part of the incident light ray to the metal core. It is thus preferably discontinuous, non-uniform, possibly consisting of particles. In the latter case, the particles are preferably arranged at intervals with a space between particles of the order of a few nanometers.

The third protective layer 5 which is optional is intended to protect the second metal layer from oxidation or wear. This layer is preferably made of a transparent dielectric material such as TiO2, SiO2, Al2O3, MgF2, AlN, Ta2O5, Si3N4, ZnS, ZnO, ZrO2, Cr2O3, Ce02, Y2O3, HfN, HfC, Hf02, La2O3, MgO , Sb2O3, SiO, Se2O3, SnO2, WO3 or in a transparent resin. This layer has a thickness between 1 and 30 nm and preferably between 1 and 10 nm.

The present invention does not exclude the introduction of intermediate layers between the metal core and the first layer and / or between the first and second layers in order to increase the adhesion between the different layers constituting the interference pigment.

As shown schematically in Figure 2, part of the incident light ray is reflected on the outer metal layer 4 while another part is transmitted and reflected on the metal core 2. The difference in path between the two reflected beams creates by interference effect, a color exhibiting nuances as a function of the angle of observation.

According to the invention, the metal core can be manufactured starting from a foil, for example gold or silver, with the outer layers deposited by CVD, PVD, electrochemistry or by non-electrolytic means, the whole being subsequently crushed. The multilayer pigment can also be manufactured starting from flakes obtained by wet or dry chemistry, or by atomization, optionally crushed before being coated.

The pigment powder thus obtained can be dispersed in an appropriate medium depending on the application. It can thus be used in formulations for paints, inks, cosmetics and, in general, in formulations for coatings.

It is also conceivable to use the pigment powder as it is. In this configuration, the powder deposited beforehand is compacted on a substrate and then sintered in a uniform or selective manner under the effect of a local supply of heat, for example by laser. This results in a dense coating covering all or part of the substrate. It is also possible to envisage producing massive parts by compaction and densification of the pigment powder. It is also conceivable to produce massive parts by additive manufacturing.

For example, in the field of watchmaking, the pigments can be used after dispersion in an appropriate medium or as such to coat or decorate a covering part (dial, bezel, middle part, back, clasp , ...) or to make a massive covering part (dial, hand, index, pusher, etc.).

Finally, it should be specified that the pigment with a pure gold core and its different layers is titratable at 18 carats. Thus, for a pigment comprising successively: a gold core with a thickness of 400 nm for a transverse diameter of 30 µm, a first coating layer of SiO2 with a thickness of 330 nm, a second metallic coating layer in Ag with a thickness of 5 nm, a third protective layer of SiO2 with a thickness of 10 nm, the mass percentage of gold is 79.01%, i.e. greater than the 75% required for 18 karat gold.

The metal core can also be produced in other precious alloys in order to achieve legal titles such as, for example, Pd500 or Pt900.

Legend of figures

[0028] (1) Interference pigment (2) Metal core (3) First layer, also called dielectric layer (4) Second layer, also called metallic layer (5) Third layer, also called protective layer D: Transverse diameter of the core metal forming a flake E: Thickness of the metallic core forming a flake

Claims (17)

1. Multilayer interference pigment (1) comprising successively: - a metallic core (2) in the form of a flake, the metallic core (2) comprising a material chosen from gold, silver, palladium, rhodium, ruthenium, platinum, osmium, l iridium and one of their alloys; - a first layer (3) of a transparent dielectric material; - a second metallic layer (4). 2. Pigment according to claim 1, wherein the metal core (2) comprises a material chosen from gold, silver, rhodium and one of their alloys and, more preferably, chosen from gold, silver. and one of their alloys. 3. Pigment according to claim 1 or 2, comprising a third protective layer (5) formed of a transparent dielectric material or of a transparent resin. 4. Pigment according to claim 3, wherein the dielectric material of the first layer (3) and of the third layer (5) is chosen from TiO2, SiO2, Al2O3, MgF2, AlN, Ta2O5, Si3N4ZnS, ZnO, ZrO2, Cr2O3, CeO2, Y2O3, HfN, HfC, HfO2, La2O3, MgO, Sb2O3, SiO, Se2O3, SnO2 and WO3. 5. Pigment according to any one of the preceding claims, in which the second metallic layer (4) comprises a material chosen from silver, gold, aluminum, titanium, palladium, platinum, ruthenium, rhodium, osmium, iridium, tin, chromium, iron, cobalt, nickel, copper, zinc, rhodium and one of their alloys. 6. Pigment according to any one of the preceding claims, in which the metal core (2) has an average transverse diameter of between 2 and 300 µm, preferably between 5 and 100 µm and more preferably between 10 and 30 µm, and a average thickness between 20 and 1000 nm and, preferably, between 300 and 500 nm. 7. Pigment according to any one of the preceding claims, in which the first layer (3) has a thickness between 50 and 500 nm and, preferably, between 300 and 400 nm. 8. Pigment according to any one of claims 4 to 7, wherein the second layer (4) and the third layer (5) have a thickness between 1 and 30 nm and, preferably, between 1 and 10 nm. 9. Pigment according to any one of the preceding claims, in which the second layer (4) is discontinuous. 10. Pigment according to any one of the preceding claims, in which the second layer (4) is in the form of particles arranged at intervals. 11. Part, in particular trim part, for watchmaking or jewelry comprising interference pigments according to any one of the preceding claims. 12. Part according to claim 11, comprising a coating comprising said interference pigments. 13. Part according to claim 11, comprising in the mass dists interference pigments. 14. Watch comprising the part according to any one of claims 11 to 13. 15. Jewel comprising the part according to one of claims 11 to 13. 16. Use of interference pigments (1) according to any one of claims 1 to 10 in paint or ink formulations. 17. Use of interference pigments (1) according to any one of claims 1 to 10 in cosmetic formulations.