CH713536A2 - Interferential pigment. - Google Patents

Abstract

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

Description

Description

TECHNICAL FIELD [0001] The present invention relates to a novel interference pigment with a more particular field of application in the fields of watchmaking, jewelery and cosmetics.

BACKGROUND [0002] The creation of a color palette by interference of reflected light on multilayer structures is well known. For example, documents EP 0 905 205 and US Pat. No. 6,626,989 disclose pearlescent pigments comprising a mica core coated with a titanium oxide layer.

[0003] More recently, interference pigments with a metal core have spread. The choice of metal at heart was mainly limited to aluminum. Although this type of pigment already has an attractive aesthetic appearance, the intensity and brilliance of interferential colors can be further improved by inter alia playing on the optical properties of the metal at heart. 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.

For this purpose, a pigment, its use and a part according to the appended claims are provided.

More specifically, the present invention provides a multilayer interference pigment comprising successively: a metal core in the form of a flake, the metal 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 metal layer.

With this metal core made of a precious metal having a high level of reflectance, and preferably greater than that of aluminum, in at least a portion of the visible spectrum, interference colors gain in brightness and intensity compared to those obtained with a conventional interference pigment. This results in coated or massive pieces having a particular brilliance appreciated in the field of watchmaking, jewelery and cosmetics.

According to particular embodiments of the invention, the interference pigment has one or a suitable combination of the following characteristics: the metal core comprises a material chosen from gold, silver, rhodium and one of their alloys and more preferably, selected from gold, silver and one of their alloys; it comprises a third protective layer formed of a transparent dielectric material or a transparent resin; the dielectric material of the first layer and of the third layer is chosen from TiO 2, SiO 2, Al 2 O 3, MgF 2, AlN, Ta 2 O 5, S 3 N 4 ZnS, ZnO, ZrO 2, Cr 2 O 3, CeO 2, Y 2 O 3, HfN, HfC, HfO 2, La 2 O 3, MgO, Sb 2 O 3, SiO, Se 2 O 3, SnO 2 and WO 3; the second metal layer comprises a material chosen from 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 a mean transverse diameter of between 2 and 300 μm, preferably between 5 and 100 μm and more preferably between 10 and 30 nm, and an average thickness of between 20 and 1000 nm and preferably between 300 and 500 μm; nm; the first layer has a thickness of between 50 and 500 nm and, preferably, between 300 and 400 nm; the second layer and the third layer have a thickness of 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.

The present invention also relates to a part and, in particular to a trim part, for the watch or jewelery including interferential pigments as described above.

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

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

It also relates to the use of the interference pigments described above in paint formulations, inks or cosmetics.

BRIEF DESCRIPTION OF THE FIGURES [0013] The invention will be described below in more detail with the aid of the accompanying drawings, given as non-limiting examples, in which:

Fig. 1 schematically shows the different layers of the interference pigment according to the invention.

Fig. 2 diagrammatically represents the optical paths of the light through the interference pigment according to the invention.

DETAILED DESCRIPTION OF THE INVENTION [0014] The present invention relates to a multilayer interference pigment comprising a core made of a pure precious metal or alloyed 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 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 has a high reflectance for wavelengths greater than 550 nm. It is therefore preferred when warm colors (red, yellow) are desired. Silver, on the other hand, has a high reflectance over a wider range of the visible spectrum, which also makes it possible to obtain bluish and green colors. In the case of an alloy, the choice is, for example, on an Ag-Pt alloy.

The pigment 1 according to the invention shown in FIG. 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 layer 5 protection.

The metal core 2 is in the form of an elongate straw having a mean 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 a mean thickness E of between 20 and 1000 nm and preferably between 300 and 500 nm. In general, the flake form factor, 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 TiO 2, SiO 2, Al 2 O 3, MgF 2, AlN, Ta 2 O 5, Si 3 N 4, ZnS, ZnO, ZrO 2, Cr 2 O 3, CeO 2, Y 2 O 3, HfN, HfC, HfO 2, La 2 O 3, MgO, Sb 2 O 3, SiO, Se 2 O 3, SnO 2, or WO 3, with a preference for SiO 2. This layer has a thickness of between 50 and 500 nm and preferably between 300 and 400 nm, the thickness and the refractive index of the dielectric material being selected according to the desired interference color.

The second layer 4 is formed of a metal or a metal alloy for reflecting light on the surface of the interference pigment. The metal is preferentially chosen from silver, gold, aluminum, titanium, palladium, platinum, ruthenium, rhodium, osmium, iridium, tin, chromium and iron. , cobalt, nickel, copper, zinc, rhodium and one of their alloys. It is more preferably chosen from silver, gold, aluminum, rhodium and one of their alloys. This layer has a thickness of between 1 and 30 nm and preferably between 1 and 10 nm. The layer is configured to allow transmission of a portion of the incident light beam to the metal core. It is thus preferentially 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 TiO 2, SiO 2, Al 2 O 3, MgF 2, AlN, Ta 2 O 3, Si 3 N 4, ZnS, ZnO, ZrO 2, Cr 2 O 3, CeO 2, Y 2 O 3, HfN, HfC, HfO 2, La 2 O 3, MgO , Sb 2 O 3, SiO, Se 2 O 3, SnO 2, WO 3 or in a transparent resin. This layer has a thickness of between 1 and 30 nm and preferably between 1 and 10 nm.

The present invention does not preclude introducing intermediate layers between the metal core and the first layer and / or between the first and second layers to increase the adhesion between the various constituent layers of the interference pigment.

As schematized in FIG. 2, a part of the incident light beam is reflected on the outer metal layer 4 while another part is transmitted and reflected on the metal core 2. The difference in trajectory between the two reflected beams interferentially creates a color with shades depending on the viewing angle.

According to the invention, the metal core can be made from a sheet, for example gold or silver, with the outer layers deposited by CVD, PVD, electrochemistry or electrolessly, the whole being subsequently crushed. The multilayer pigment may also be manufactured from flakes obtained by wet or dry chemistry or by spraying, optionally crushed before being coated.

Claims (15)

The pigment powder thus obtained can be dispersed in a suitable medium depending on the application. It can thus be used in formulations for paints, inks, cosmetics and, in general, in coating formulations. It is also possible to use the pigment powder as it is. In this configuration, the previously deposited powder is compacted on a substrate and then sintered uniformly or selectively under the effect of a local heat input for example by laser. This results in a dense coating covering all or part of the substrate. It is also conceivable to produce solid parts by compaction and densification of the pigment powder. It is also conceivable to produce massive pieces by additive manufacturing. For example, in the field of horology, the pigments can be used after dispersion in a suitable medium or as such to coat or decorate a piece of clothing (dial, bezel, middle part, bottom, clasp , ...) or to make a massive piece of clothing (dial, needle, index, pusher, etc.). Finally, we will specify that the pigment with a pure gold heart and its different layers is titrable to 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 SiO2 coating layer with a thickness of 330 nm, a second metal layer coating material with a thickness of 5 nm, - a third SiO2 protective layer with a thickness of 10 nm, the mass percentage of the gold is 79.01%, i.e. higher than the 75% required for 18-carat gold. The metal core can also be made in other precious alloys to achieve legal titles such as, for example, the Pd500 or Pt900. Legend of Figures [0028] (1) Interference Pigment (2) Metallic core (3) First layer, also called dielectric layer (4) Second layer, also called metal layer (5) Third layer, also called protective layer D: Diameter cross-section of the metallic core forming a flake E: Thickness of the metallic core forming a spangle Claim 1. multilayer interference pigment (1) successively comprising: a metal core (2) in the form of a flake, the metal 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 layer (4) metal. 2. Pigment according to claim 1, wherein the metal core (2) comprises a material selected from gold, silver, rhodium and one of their alloys and, more preferably, selected from gold, silver and one of their alloys. 3. Pigment according to claim 1 or 2, comprising a third layer (5) of protection formed of a transparent dielectric material or a transparent resin. 4. 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. Pigment according to any one of the preceding claims, wherein the second layer (4) metal comprises a material selected from silver, gold, aluminum, titanium, palladium, platinum, ruthenium, rhodium, osmium, iridium, tin, chromium, iron, cobalt, nickel, copper, zinc, rhodium and one of their alloys. Pigment according to any one of the preceding claims, wherein the metal core (2) has a mean transverse diameter of between 2 and 300 μm, preferably between 5 and 100 μm and more preferably between 10 and 30 μm, and average thickness of between 20 and 1000 nm and preferably between 300 and 500 nm. 7. Pigment according to any one of the preceding claims, wherein 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 the preceding claims, wherein the second layer (4) and the third layer (5) have a thickness of between 1 and 30 nm and preferably between 1 and 10 nm. 9. Pigment according to any one of the preceding claims, wherein the second layer (4) is discontinuous. 10. Pigment according to any one of the preceding claims, wherein the second layer (4) is in the form of particles arranged at intervals. 11. Room and, in particular a dressing room, for the watch or jewelery industry comprising interferential pigments according to any one of the preceding claims. 12. Part according to claim 11, comprising a coating comprising interferential pigments. 13. Part according to claim 11, comprising in bulk interference pigments. 14. Watch or jewel comprising the part according to any one of claims 11 to 13. 15. Use of interferential pigments (1) according to any one of claims 1 to 10 in formulations of paints, inks or cosmetics.