EP4528390A1 - Method for manufacturing an enamelled timepiece component - Google Patents

Abstract

One aspect of the invention relates to a method of manufacturing a watch component (2) comprising a colored enamel coating (10), the method comprising the following steps:
- provision (20) of a substrate chosen from materials capable of withstanding an enamel firing temperature;
- preparation (22) of a colored enamel composition constituting the colored enamel coating of said watch component (2), said step (22) providing for the production of an encapsulation (24) of color pigments in transparent protective shells of inorganic material and the production of a mixture (25) of said encapsulated color pigments with an enamel preparation;
- application (27) of at least one layer of colored enamel composition prepared on a receiving zone (8) included on the substrate;
- firing (28) of said layer of colored enamel composition included in this receiving zone (8).

Description

Technical field of the invention

The present invention relates to a method of manufacturing a watch component comprising an enamel coating incorporating color pigments.

The invention also relates to the watch component provided with such an enamel coating and to a timepiece, such as a watch, comprising such a watch component.

Technological background

In the field of watchmaking, watch components with an enamel coating, such as enamel dials, have been known for a very long time. Such enamel dials have interesting characteristics, insofar as they are practically unalterable and allow for the creation of decorations with a palette of extremely vivid and rich colors including color pigments containing Cadmium or Selenium.

However, such colour pigments no longer meet the criteria for approval for watchmaking due to their toxicity.

It is therefore understandable that there is a need to find an alternative solution to the state of the art.

Summary of the invention

The invention aims in particular to overcome the various drawbacks of the state of the art.

Another aim of the invention is to obtain a watch component comprising an enamel coating comprising non-toxic colored pigments, in particular brightly colored pigments.

• mise à disposition d'un substrat choisi parmi des matériaux capables de résister à une température de cuisson d'émail ;
• préparation d'une composition d'émail coloré constituant le revêtement en émail coloré dudit composant horloger, ladite étape prévoyant la réalisation d'une encapsulation de pigments de couleur dans des coques protectrices transparentes de matière inorganique et la réalisation d'un mélange desdits pigments de couleur encapsulés avec une préparation d'émail ;
• application d'au moins une couche de composition d'émail coloré préparée sur une zone de réception comprise sur le substrat ;
• cuisson de ladite couche de composition d'émail coloré comprise dans cette zone de réception.

For this purpose, one aspect of the invention relates to a method of manufacturing a watch component comprising a colored enamel coating, the method comprising the following steps:

• provision of a substrate chosen from materials capable of withstanding an enamel firing temperature;
• preparation of a colored enamel composition constituting the colored enamel coating of said watch component, said step providing for the encapsulation of color pigments in transparent protective shells of inorganic material and the production of a mixture of said encapsulated color pigments with an enamel preparation;
• applying at least one layer of prepared colored enamel composition to a receiving area included on the substrate;
• firing said layer of colored enamel composition included in this receiving area.

• lors de l'encapsulation un processus de formation d'une couche homogène et conforme de matière est réalisé sur la surface entière de chaque pigment de couleur, ladite matière étant constituée par un oxyde métallique ;
• le processus de formation est effectuée à partir d'une technologie ALD et/ou d'une technologie de microémulsion ;
• la composition d'émail coloré comprend pourcentage massique d'au plus de 30% de pigments de couleur encapsulés ;
• la composition d'émail coloré comprend pourcentage massique d'au plus de 50% de pigments de couleur encapsulés ;
• une étape de traitement de ladite zone de réception du substrat sur laquelle est appliquée la couche de composition d'émail coloré, ladite étape prévoyant l'application d'agents dégraissant et/ou d'adhésion sur cette zone de réception ;
• une étape de finalisation/terminaison du substrat pourvu sur sa zone de réception de la couche de composition d'émail coloré, ladite étape comprenant des sous-étapes de lapidage et de polissage ;
• chaque pigment est un pigment de couleur vive ;
• chaque pigment de couleur est un pigment inorganique ou un pigment inorganique non-toxique.

In other embodiments:

• during encapsulation a process of forming a homogeneous and conformal layer of material is carried out on the entire surface of each color pigment, said material being constituted by a metal oxide;
• the forming process is carried out using ALD technology and/or microemulsion technology;
• the composition of colored enamel comprises a mass percentage of at most 30% of encapsulated color pigments;
• the composition of colored enamel comprises a mass percentage of at most 50% of encapsulated color pigments;
• a step of treating said receiving area of the substrate on which the layer of colored enamel composition is applied, said step providing for the application of degreasing and/or adhesion agents on this receiving area;
• a step of finalizing/terminating the substrate provided on its receiving area with the layer of colored enamel composition, said step comprising sub-steps of stoning and polishing;
• each pigment is a brightly colored pigment;
• Each color pigment is an inorganic pigment or a non-toxic inorganic pigment.

Another aspect of the invention relates to a watch component capable of being obtained from this method.

Advantageously, this watch component comprises a substrate chosen from materials configured to withstand an enamel firing temperature and a receiving zone of which comprises a colored enamel coating including encapsulated inorganic and non-toxic brightly colored pigments.

Advantageously also, the watch component includes a coating forming a decorative element.

Another aspect of the invention also relates to a timepiece comprising such a timepiece component.

Brief description of the figures

• la figure 1 est une représentation schématique d'une pièce d'horlogerie comprenant un composant horloger tel qu'un cadran, pourvu d'un revêtement en émail coloré, selon un mode de réalisation de l'invention, et
• la figure 2 représente un logigramme relatif à un procédé de fabrication d'un composant horloger tel que le cadran comprenant le revêtement émaillé incorporant des pigments de couleur vive, selon un mode de réalisation de l'invention.

Other features and advantages of the invention will become more clearly apparent from reading the following description of a method of particular embodiment of the invention, given as a simple illustrative and non-limiting example, and the appended figures, among which:

• there Figure 1 is a schematic representation of a timepiece comprising a timepiece component such as a dial, provided with a colored enamel coating, according to one embodiment of the invention, and
• there Figure 2 represents a flowchart relating to a method of manufacturing a watch component such as the dial comprising the enamel coating incorporating brightly colored pigments, according to one embodiment of the invention.

Detailed description of the invention

In reference to the figures 1 And 2 , the invention relates to a method for manufacturing a watch component 2 comprising a colored enamel coating. Such a method helps to obtain a watch component 2 of a timepiece 1, comprising a substrate provided with a receiving zone 8 including this enameled coating incorporating brightly colored pigments. This receiving zone 8 included on the external surface of the substrate/watch component 2, can include all the faces of the substrate/watch component 2 or just a single face or even one or more distinct portions of a single face or of several different faces. Thus in these different variants, this coating 10 can help to form a decorative element on this watch component 2.

In reference to the Figure 1 and for a better understanding of the invention, the watch component 2 is here a decorative element such as a dial 2 of the timepiece 1. This dial 2 comprises on its visible face 9 the coating 10 in colored enamel located in its receiving zone 8. It will be noted however that this watch component 2 can alternatively be another decorative element such as for example a bezel, a moon phase, a date disc 7, a dial index, etc.

In this embodiment, the timepiece, which may be a wristwatch, comprises the dial 2 with an analog display, hour hands 3a, minute hands 3b and second hands 3c which are capable of moving opposite time indexes 5 inscribed on an hour circle 4. In the example shown, the dial 2 comprises an aperture 6 crossing the entire thickness of this dial 2 and below which a date disc 7 moves.

In this context, such a manufacturing method comprises a step 20 of making available, or even of supplying, the substrate to form this watch component 2. Such a step 20 may comprise a sub-step 21 of cutting the substrate into a plate, to the dimensions of the watch component 2 to be manufactured, said plate being able to have a thickness appropriate for this component 2. This plate, and therefore this substrate, is made of a material configured to be able to withstand enamel firing temperatures. These temperatures are preferably greater than 500 degrees Celsius or even temperatures between 700 degrees Celsius and 1300 degrees Celsius. For example, this material may be metallic or a metal alloy, for example steel, or even ceramic.

Such a material can also be transparent, such as a monocrystalline or polycrystalline material, for example quartz, spinel or corundum, notably sapphire. An amorphous material, such as mineral glass, can also be used, provided that its softening point is higher than the enamel firing temperature.

This method then comprises a step 22 of preparing a colored enamel composition. This step 22 then comprises a sub-step 23 of preparing an enamel preparation. In particular, it may be a sub-step 23 of preparing a colorless, colored, translucent or transparent enamel preparation. This sub-step 23 of preparation is carried out on the basis of well-known operating methods and preparation processes of the state of the art that we will not detail here and which make it possible to obtain an enamel preparation that is colorless, colored, translucent or transparent. It should be noted in particular that the development of this preparation is carried out with a water or oil base which is mixed with enamel. In addition, the preparation of colorless or colored enamel is also called " initial composition of colorless or colored enamel ".

This step 22 then comprises a sub-step 24 of encapsulating colored pigments in transparent protective shells of inorganic material also called “transparent protective envelopes of inorganic material”. Such a sub-step 24 provides for encapsulating each pigment intended for the colored enamel composition in such a transparent protective shell in order in particular to improve the thermal and/or chemical stability property of this pigment. Indeed, this improvement in thermal stability allows each encapsulated pigment to retain its intact crystallographic structure when the temperature of the medium in which it evolves rises to the enamel firing temperature.

Such pigments are preferably brightly colored or vibrant colors such as red, yellow, orange, green, pink or blue and their variants. A bright color is understood to mean a color that is intense with in the CIELAB color space in transmission mode of the standardized illuminant D65 with an observer of 10° and a measurement geometry d:0°, (in accordance with CIE standards No. 15, ISO 7724/1, DIN 5033 Teil 7, ASTM E-1164) with an L* component greater than 40. It should be noted here that CIELAB is a CIE 1976 L*a*b* color space corresponding to a color space particularly used for the characterization of surface colors.

In this embodiment of the invention, these color pigments are inorganic pigments. In particular, these pigments are non-toxic inorganic pigments. Such pigments belong in a non-limiting and non-exhaustive manner to the family of (oxy)nitrides, to the cerium sulfide family or even the phosphate family. It should be noted that pigments in the (oxy)nitride family typically have a bright color ranging from red to green and from blue to yellow. Regarding pigments belonging to the cerium sulfide family, they essentially have bright colors ranging from red to orange. And regarding pigments in the phosphate family, they have bright blue, green or even violet colors.

This encapsulation sub-step 24 provides a process for forming/producing a homogeneous and conformal layer of material on the entire surface of each pigment, said material being constituted by a metal oxide. To do this, at least one deposit of this material is then made on this surface in order to produce such a layer. In this context, this layer then forms the protective shell encapsulating each pigment. It is understood that the cycle of deposition of this material on this surface can be configured so as to obtain a determined thickness of this layer. Indeed, this thickness of the layer can vary according to the characteristics of the preparation of colorless enamel and/or according to the characteristics of the colored enamel coating to be produced on the watch component 2.

It is understood that such a layer is of course transparent so as not to alter the intrinsic color of the brightly colored pigment.

The metal oxide constituting the homogeneous and conformal layer of material may be, in a non-limiting and non-exhaustive manner: a silicon dioxide of formula SiO ₂ , an aluminum oxide of formula Al ₂ O ₃ , a zinc oxide of formula ZnO or even a titanium oxide of formula TiO ₂ .

This encapsulation sub-step 24 provides that the formation of the layer and therefore of this protective shell encapsulating each pigment, can be carried out for example using a technology for depositing at least one atomic layer, better known by the English acronym ALD for “ Atomic Layer Deposition ”. In the context of the invention, this technology allows therefore to carry out a deposit of a thin layer on the surface of each color pigment on the basis of chain reactions in the gas phase from metal oxide precursors such as for example trimethylaluminum when the metal oxide is an aluminum oxide.

In a variant, the formation of the layer encapsulating each pigment can be carried out using microemulsion technology. This technology makes it possible, by microemulsion reaction, to deposit a metal oxide on the surface of the pigment from a precursor of this metal oxide. In the context of the invention, this precursor can be a tetraethyl orthosilicate when the metal oxide is a silicon dioxide.

In another variant, this formation of the layer encapsulating each pigment can be carried out on the basis of the combination of these two technologies. For example, this formation can, without limitation, begin with the implementation of ALD technology and continue with microemulsion technology.

• son homogénéité ;
• sa conformité ;
• une épaisseur comprise entre 2 nm et 1000 nm, de préférence 10 nm ou de préférence 30 nm ou encore de préférence 50 nm;
• sa rigidité ; et/ou
• sa transparence.

It is understood that such a sub-step 24 thus participates in encapsulating each pigment in a protective shell formed by the transparent layer of material which is included on the surface of the pigment. Such a layer is characterized by:

• its homogeneity;
• its conformity;
• a thickness between 2 nm and 1000 nm, preferably 10 nm or preferably 30 nm or even preferably 50 nm;
• its rigidity; and/or
• its transparency.

• l'oxydation à la température de cuisson de l'émail ;
• un milieu acide notamment acide léger avec un pH ≃ 4.5 ;
• une exposition aux rayonnements ultraviolets ;
• des agents cosmétiques.

Furthermore, it should be noted that this layer, and therefore the shell, provides effective protection to the color pigment against, simultaneously:

• oxidation at the firing temperature of the enamel;
• an acidic environment, particularly a mild acid with a pH ≃ 4.5;
• exposure to ultraviolet radiation;
• cosmetic agents.

The preparation step 22 of the colored enamel composition also comprises a sub-step 25 of mixing said encapsulated color pigments with the colorless enamel preparation. This mixing sub-step 25 contributes to obtaining the colored enamel composition in which the encapsulated color pigments are then dispersed. During this sub-step 25, the mixture obtained, corresponding to the colored enamel composition, comprises a mass percentage of at most 30% or at most 50% of encapsulated color pigments.

This mass percentage can preferably be between 2% and 30%.

Such a mass percentage may also preferably be between 5% and 30%.

Such a mass percentage may also preferably be between 5% and 10%.

It is understood that these mass percentages of color pigments contribute to establishing compromises in this mixture between color, transparency and color intensity while guaranteeing good final properties (e.g.: mechanical, homogeneity, etc.).

Furthermore, it will be noted that this mixing can be done by liquid means or by any other mixing means known to those skilled in the art.

Subsequently, the method comprises a step 26 of treating said receiving zone 8 of the substrate on which the colored enamel coating will be produced. During such a step 26, degreasing agents and/or adhesion can be applied to this reception area 8 intended to include this coating 10.

The method then comprises a step 27 of applying at least one layer of colored enamel composition thus prepared onto the receiving area 8 of the substrate. It is understood that the receiving area 8 may for example be in whole or in part the visible face 9 of this timepiece component 2 when it is mounted in the timepiece 1. During this step 27, the layer of colored enamel composition may be deposited onto this receiving area 8 by spraying, projection and/or printing.

The method then comprises a step 28 of firing said at least one layer of colored enamel composition included in the receiving zone 8 of the substrate. During this step, the substrate is fired at a temperature of between 300 degrees and 1200 degrees, preferably between 500 degrees and 800 degrees, preferably at 690 degrees with a hold of between 1 and 10 minutes, preferably 5 minutes. Such a firing step 28 is carried out in air or in a controlled atmosphere, for example under argon, nitrogen or even under vacuum.

It will be noted that this step 28 may provide a sub-step 29 of drying the layer of colored enamel composition covering the receiving zone 8 of the substrate before proceeding with its firing. Such a sub-step 29 helps to eliminate the possible presence of water in the layer before this firing. All the usual drying methods can be used, for example in the open air, in an oven or by radiation.

It will be noted that the succession of application steps 27 and firing steps 28 of the method can be repeated if necessary in order to obtain a determined or desired thickness of the colored enamel coating on the receiving zone 8 and on the watch component 2. In this context, this thickness is a function of the number of layers constituting the colored enamel coating 8. It is understood that this thickness is notably defined according to characteristics of the colored enamel coating to be applied to the watch component 2, in particular aesthetic characteristics.

The method also comprises a step 30 of finalizing/terminating the substrate provided on the receiving area of the baked colored enamel composition layer in order to obtain this watch component 2 comprising the colored enamel coating 10. This step 30 may then comprise a sub-step 31 of lapping this substrate and in particular of the baked colored enamel composition layer. This sub-step 31 may be carried out until a desired regular thickness of the colored enamel coating 10 is obtained. This step 30 also subsequently comprises a sub-step 32 of polishing or texturizing this substrate and in particular of the baked colored enamel composition layer frosted during the lapping sub-step 31.

In addition, this step 30 may also provide a sub-step 33 of machining this substrate aimed at sizing it if necessary for its assembly in the timepiece 1.

It will be noted that when this watch component is dial 2, machining operations of this dial 2 can be carried out in order to create a through opening for the passage of a drive shaft of the hands 3a to 3c. In this context, operations for producing appliques/indexes if this has not already been done can also be carried out. These appliques can be directly drawn, driven or glued onto the visible face or even glued via parts passing through this dial 2 via holes created during the machining operation.

The above description corresponds to a preferred embodiment and should in no case be considered limiting, more particularly with regard to the type of color pigments used for coloring the enamel. Indeed, other color pigments other than bright colors are also part of the invention.

Nomenclature

• 1. Timepiece
• 2. Watch component such as a dial
• 3a. Hour hand
• 3b. Minute hand
• 3c. Second hand
• 4. Timetable index
• 5. Hour tower
• 6. Counter
• 7. Date disc
• 8. Receiving area for the substrate and the watch component
• 9. Visible face of the watch component
• 10. Colored enamel coating

Claims (13)

Method for manufacturing a watch component (2) comprising a colored enamel coating (10), the method comprising the following steps: - provision (20) of a substrate chosen from materials capable of withstanding an enamel firing temperature; - preparation (22) of a colored enamel composition constituting the colored enamel coating of said watch component (2), said step (22) providing for the production of an encapsulation (24) of color pigments in transparent protective shells of inorganic material and the production of a mixture (25) of said encapsulated color pigments with an enamel preparation; - application (27) of at least one layer of colored enamel composition prepared on a receiving zone (8) included on the substrate; - firing (28) of said layer of colored enamel composition included in this receiving zone (8). Method according to the preceding claim, in which during encapsulation a process of forming a homogeneous and conformal layer of material is carried out on the entire surface of each color pigment, said material being constituted by a metal oxide. Method according to the preceding claim, wherein the forming process is carried out using ALD technology and/or microemulsion technology. A method according to any preceding claim, wherein the colored enamel composition comprises a mass percentage of at most 30% of encapsulated color pigments. A method according to any one of claims 1 to 3, wherein the colored enamel composition comprises a mass percentage of at most 50% of encapsulated color pigments. Method according to any one of the preceding claims, comprising a step of treating (26) said receiving area of the substrate on which the layer of colored enamel composition is applied, said step (26) providing for the application of degreasing and/or adhesion agents on this receiving area. Method according to any one of the preceding claims, comprising a step of finalizing/terminating (30) the substrate provided on its receiving zone (8) with the layer of colored enamel composition, said step (30) comprising sub-steps of stoning (31) and polishing (32). A method according to any preceding claim wherein each pigment is a brightly colored pigment. A method according to any preceding claim wherein each color pigment is an inorganic pigment or a non-toxic inorganic pigment. Watch component (2) capable of being obtained from the method according to any one of the preceding claims. Watch component (2) according to the preceding claim, comprising a substrate chosen from materials configured to withstand an enamel firing temperature and a receiving zone (8) of which comprises a colored enamel coating including encapsulated inorganic and non-toxic brightly colored pigments. Watch component (2) according to any one of claims 10 and 11, in which said coating (8) forms a decorative element. Timepiece (1) comprising a timepiece component (2) according to any one of claims 10 to 12.

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