CH712263A2 - Mother-of-pearl substrate coated with a blue layer. - Google Patents

Abstract

The present invention relates to a process for coating a mother-of-pearl substrate (1) intended for the watch industry or the jewelery industry, said method comprising a step of vacuum deposition of a layer (3) of tungsten oxide . Timepiece or jewelery part comprising a mother-of-pearl substrate (1) provided on a surface with a blue coating comprising a layer (3) of tungsten oxide.

Description

Description

OBJECT OF THE INVENTION

The present invention relates to the field of watchmaking and jewelery. More particularly, it relates to a method for depositing a blue layer on a mother-of-pearl substrate and to the part comprising said coated substrate.

TECHNOLOGICAL BACKGROUND AND STATE OF THE ART

The aesthetic aspect being important in the watch industry, it is appreciated to color some components. We think in particular of watch dials that we like to color in different colors and, among others, in blue that reminds us of the color of the sapphire or the sea.

The use of inorganic thin layers to color the surfaces of timepieces is well established. In order to deposit thin layers of blue color, the following compositions are typically used: carbo-oxynitrides of Ti and / or Zr; (Ti, Zr) C, O, N; TiAlN. These layers have the characteristic of absorbing light and being practically opaque from a thickness of a few tens of nanometers. They also have the characteristic of strongly reflecting the light, which gives them a metallic appearance.

These two characteristics are detrimental when one wants to maintain the original appearance, whether it is a pattern, a texture or an interference effect, of the visible substrate after deposition of the coloring layer. This is particularly true for mother-of-pearl substrates that have very attractive iridescent reflections that it would be a shame to camouflage after coating.

For mother-of-pearl dials, the document EP 1 672 436 proposes a manufacturing process where a mother-of-pearl plate is subjected to a sanding operation to reveal the particular morphology of the mother-of-pearl. Then, the sanded substrate is coated with a metal layer or oxide, nitride or metal carbide. This document mentions the need to control the thickness of the coating in order to keep the morphology of the mother-of-pearl as accurately as possible after deposit, but does not mention a solution for depositing a blue transparent layer.

Various solutions can be envisaged for depositing thin layers of blue color that are transparent.

For example, the following chemical compositions: sub-stoichiometric TiO 2, CoSiO 3, Al 2 CoO 4 and various silicates and aluminates of Co and Cu form after deposition a transparent blue layer. However, the disadvantage of these compositions is that they do not have sufficient coloring power in thin layers.

Another solution is to deposit several dielectric layers, e.g. SiO2 or Si3N4, creating a blue appearance by interference. This solution, however, has the disadvantage that the color displayed will be dependent on the angle of view.

It is also possible to deposit layers of known organic pigments to form a transparent layer but with the disadvantage that the behavior in time of the color is poor.

SUMMARY OF THE INVENTION

The present invention provides a novel dyeing method suitable for a mother-of-pearl substrate. More specifically, the object of the invention is to develop a method for the deposition of a blue layer which is transparent while having sufficient dye power in a thin layer.

For this purpose, a method and a timepiece or jewelery according to the appended claims are proposed. BRIEF DESCRIPTION OF THE FIGURES

The features and advantages of the present invention will appear on reading the detailed description below with reference to FIG. 1.

Schematically, FIG. 1 represents according to the invention the stack of different layers on the substrate. Legend [0014] (1) Substrate (2) Intermediate layer between the substrate and the WOy layer (3) WOy layer (4) Coat deposited on the WOy layer

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for depositing a blue layer on a mother-of-pearl substrate which is a timepiece or a jewelery piece. More specifically, the substrate may be a mother-of-pearl dial in the case of watchmaking.

The coloration is performed by depositing an intrinsically blue layer in transmission and transparent. According to the invention, this layer is composed of tungsten oxide which, thanks to its transparency, does not suppress the visual effects of the surface below. It may be the iridescent reflections of the mother-of-pearl, a texture including brushing or polishing, or interferential effects induced by the deposition of intermediate layers between the substrate and the blue layer.

The hue and saturation of the color are a function of the O / W ratio of the tungsten oxide and the thickness of the layer. To obtain the blue color, the tungsten oxide WOy is selected with a value y of between 2.5 and 2.99, preferably between 2.5 and 2.9, and more preferably between 2.5 and 2.6. Then, the thickness is chosen between 20 and 2000 nm so that the blue color of the layer is sufficiently saturated. Optionally, the tungsten oxide may be doped with other metals, for example with lithium, to increase the saturation of the color.

The tungsten oxide layer is deposited under vacuum by physical vapor deposition (PVD) using one of the techniques grouped under the generic term PVD, namely cathode sputtering, ion beam sputtering, ion sputtering. evaporation or laser ablation.

To improve the grip, the PVD deposition of tungsten oxide may be preceded by a plasma treatment under oxygen and argon. In addition and always optionally, additional transparent or semi-transparent layers may be deposited above and / or below the tungsten oxide layer. Thus, as schematized in FIG. 1, the substrate 1 may, in addition to the tungsten oxide layer 3, comprise an intermediate layer 2. This layer can have several functions. It can be used to promote the hooking of the WOy layer on the substrate. Another function may be to adjust the reflection color by interferential effect. For this purpose, the layer 2 may be monolayer or formed of a stack of layers with alternating layers of low and high refractive index in order to obtain the desired interference effect, one or more of these layers being absorbent.

By way of example, it is possible to use a stack of SiO.sub.2 layer: index of 1.46 (low) and of Si.sub.3N.sub.4 layer: index of 2 (high). Layer thicknesses for each of them will preferably be chosen between 10 and 400 nm. The refractive index and the thickness of the layers make it possible to control the interference phenomenon, namely the amplitude and the wavelength of the constructive and destructive interference.

It will be noted that the WOy layer participates in the same manner in the stack as the other layers, according to the same interference laws. The WOy layer can therefore be used as part of these stacks to create additional interference effects. In other words, we can create (using optical simulation software) stacks with WOy and low and high index layers, which allow unattainable optical properties using only a WOy layer.

According to the invention, the materials of the intermediate layer 2 are chosen from nitrides, oxynitrides and / or oxides of silicon and / or metal and in particular from the following metals: Ti, Al, Ta, Ce, Zr, Hf.

The coating may further comprise an upper layer 4, that is to say a layer deposited on the free surface of the layer 3 of tungsten oxide. This upper layer can also fulfill one or more functions. Its function may be to increase the mechanical and chemical resistance of the coating, to give a glossy or matte appearance to the coating and / or to give a depth effect. As for layer 2, it can also have the function of adjusting the color by interference effect. It may be monolayer or multilayer (stack of alternating layers of SiO 2 and Si 3 N 4) as described for layer 2 and likewise be formed of nitrides and / or oxides of various materials.

According to the invention, the layers 2 and 4 each have a thickness between 20 and 2000 nm, the thickness being that of the monolayer if a single layer is deposited or the multilayer in the opposite case.

The blue layer deposited on the mother of pearl substrate according to the invention thus has several advantages: - The color is blue regardless of the angle of view. It is possible to modulate the hue and intensity of this color by depositing interference layers and adjusting the thickness of the tungsten oxide layer or its composition. - The particular morphology of mother-of-pearl is always visible after deposit. - The layer adheres well to the substrate, the adhesion can be further improved through the plasma treatment and deposition of interference layers. - The reflectance is low, comparable to that of dielectric oxides, to avoid the metallic appearance. - The coating is nontoxic. - The coating is stable to the conditions of production and use of the coated article (washing, mounting of the sconces, handling, etc.). - The coating is deposited under conditions that do not degrade the substrate. - The coating is chemically stable and withstands the usual tests for internal cladding in the watch industry (UV, wet heat, thermal shock, etc.).

Claims (16)

claims 1. Method for coating a mother-of-pearl substrate (1) intended for the watch-making or jewelery industry, said method comprising a step of vacuum deposition of a layer (3) of tungsten oxide. 2. Method according to claim 1, wherein the tungsten oxide of formula WOy has a y between 2.5 and 2.99, preferably between 2.5 and 2.9, and more preferably between 2.5 and 2.6, to give a blue color to said layer. (3). The method of claim 1 or 2, wherein the tungsten oxide is doped with lithium to saturate the color. 4. Method according to any one of the preceding claims, wherein the vacuum deposition of the layer (3) of tungsten oxide is preceded by a plasma treatment under argon and oxygen to improve the grip of said layer. (3) on the substrate (1). A method according to any one of the preceding claims, wherein an additional transparent or semi-transparent layer (2,4) is deposited between the substrate (1) and the tungsten oxide layer (3) and / or on the free surface of the layer (3) of tungsten oxide. 6. The method of claim 5, wherein the additional layer (2,4) is formed of a single layer or a stack of layers. The method according to claim 6, wherein said layer is formed of a stack of alternating layers of a layer with a given refractive index and a layer having a refractive index greater than the given index to create an interference effect. The method of any one of claims 5 to 7, wherein said additional layer (2,4) is composed of nitrides, oxynitrides and / or metal oxides or silicon. 9. The method of claim 8, wherein the metals of the oxides and nitrides are selected from the list consisting of titanium, tantalum, aluminum, zirconium, hafnium and cerium. 10. A method according to any one of the preceding claims, wherein the tungsten oxide layer and the additional layer (2,4) each have a thickness between 20 and 2000 nm. 11. Timepiece or jewelery part comprising a mother-of-pearl substrate (1) provided on a surface with a blue coating comprising a layer (3) of tungsten oxide. 12. Part according to claim 11, wherein the tungsten oxide of formula WOy has a value of between 2.5 and 2.99. 13. Part according to claim 11 or 12, wherein the tungsten oxide is doped with lithium to saturate the color. 14. Part according to any one of claims 11 to 13, wherein said coating further comprises an additional layer (2,4) disposed between the substrate (1) and the layer (3) of tungsten oxide and / or on the free surface of the layer (3) of tungsten oxide, said additional layer (2,4) being composed of nitrides, oxynitrides and / or metal oxides or silicon. 15. Part according to any one of claims 11 to 14, wherein each layer (2, 3, 4) has a thickness between 20 and 2000 nm. 16. Part according to any one of claims 11 to 15, wherein the substrate (1) is a dial.