Method for producing enamel timepiece parts

Abstract

One aspect of the invention relates to a method for manufacturing a timepiece component (2) comprising a colored enamel coating (10), said method comprising the following steps: a providing step (20) of providing a substrate selected from materials capable of withstanding the enamel firing temperature; a preparation step (22) of a coloured enamel composition constituting a coloured enamel coating of the timepiece part (2), said preparation step (22) comprising an encapsulation sub-step (24) of encapsulating a coloured pigment in a transparent protective shell made of an inorganic material and a mixing sub-step (25) of mixing the encapsulated coloured pigment with an enamel preparation; a step (27) of applying at least one layer of the prepared colored enamel composition to the receiving area (8) on the substrate; a firing step (28) of firing the colored enamel composition layer included in the receiving area (8).

Description

Technical Field

[0001] The invention relates to a method for producing a timepiece component comprising an enamel coating containing colour pigments.

[0002] The invention also relates to a timepiece component featuring such an enamel coating and to a timepiece, such as a watch, comprising such a timepiece component. Background Art

[0003] In the field of horology, watch parts including enamel coatings, such as enameled watch dials, have long been known. Such enamel watch dials have the interesting property that they are virtually unalterable and can be used to create decorations with extremely bright and rich colors, including cadmium- or even selenium-containing color pigments.

[0004] However, due to its toxicity, this color pigment no longer meets the certification standards for watch exterior parts.

[0005] Therefore, there is a clear need to find alternative solutions to the existing technologies. Summary of the invention

[0006] The object of the present invention is in particular to remedy the various drawbacks of the prior art.

[0007] The invention also aims to obtain a timepiece component comprising an enamel coating containing non-toxic colour pigments, in particular bright colour pigments.

[0008] To this end, one aspect of the invention relates to a method for producing a timepiece component comprising a colored enamel coating, the method comprising the following steps:

[0009] - a step of providing a substrate selected from materials capable of withstanding the enamel firing temperature;

[0010] - a step of preparing a colored enamel composition constituting the colored enamel coating of the watch component, the step of preparing comprising a sub-step of encapsulating the colored pigment in a transparent protective shell made of an inorganic material and a sub-step of mixing the encapsulated colored pigment with an enamel preparation;

[0011] - an application step of applying at least one layer of the prepared colored enamel composition to a receiving area on said substrate;

[0012] - A firing step of firing the colored enamel composition layer included in the receiving area.

[0013] In other embodiments:

[0014] - in the encapsulation sub-step, applying a forming process of forming a uniform and consistent material layer to the entire surface of each color pigment, the material of the material layer being made of metal oxide;

[0015] - the forming process is performed using ALD technology and / or microemulsification technology;

[0016] - the colored enamel composition contains up to 30% by mass of encapsulated colored pigments;

[0017] - the colored enamel composition comprises at most 50% by mass of encapsulated colored pigments;

[0018] - the method comprises a treatment step of treating said receiving area on the substrate to which the layer of colored enamel composition is applied, said treatment step comprising applying a degreasing agent and / or a bonding agent to said receiving area;

[0019] - the method comprises a final machining / finishing step of final machining / finishing said substrate in a receiving zone of said substrate for receiving a layer of colored enamel composition, said final machining / finishing step comprising a gem cutting sub-step and a polishing sub-step;

[0020] - Each color pigment is a bright color pigment;

[0021] -Every color pigment is inorganic pigment or non-toxic inorganic pigment.

[0022] Another aspect of the invention relates to a timepiece component obtainable using this method.

[0023] Advantageously, the timepiece component comprises a substrate selected from materials configured to withstand enamel firing temperatures, the receiving area on the substrate comprising a colored enamel coating containing encapsulated inorganic non-toxic pigments of vivid colors.

[0024] It is also advantageous if the timepiece component comprises an enamel coating forming a decorative element.

[0025] Another aspect of the invention also relates to a timepiece comprising said timepiece component. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features and advantages of the invention will become more apparent upon reading the following description of specific embodiments of the invention, provided purely as illustrative and non-limiting examples, and the accompanying drawings, in which:

[0027] - Figure 1 is a schematic diagram of a timepiece according to an embodiment of the present invention, the timepiece comprising a timepiece component, such as a dial, having a colored enamel coating;

[0028] - Figure 2 A flow chart showing a method for manufacturing a timepiece component according to one embodiment of the present invention, the timepiece component comprising an enamel coating containing a bright pigment, the timepiece component being, for example, a dial. DETAILED DESCRIPTION

[0029] refer to Figure 1 and 2 The present invention relates to a method for manufacturing a timepiece component 2 comprising a colored enamel coating. This method is used to obtain a timepiece component 2 for a timepiece 1, the timepiece 1 comprising a substrate provided with a receiving area 8 comprising an enamel coating containing a vivid pigment. This receiving area 8 is located on the outer surface of the substrate / timepiece component 2 and may comprise all the faces of the substrate / timepiece component 2 or only one face, or even one or more independent parts of a single face or of one or more different faces. Thus, in these different variants, the colored enamel coating 10 can participate in forming a decorative element on the timepiece component 2.

[0030] refer to Figure 1 For a better understanding of the invention, the timepiece component 2 is in this example an external component, such as a dial 2 of a timepiece 1. The dial 2 comprises, on its visible face 9, a colored enamel coating 10 in its receiving area 8. However, it should be noted that the timepiece component 2 may also be another external component, such as a bezel, a moon phase, a date disc 7, a dial hand, etc.

[0031] In this embodiment, the timepiece may be a wristwatch comprising an analog display dial 2, hour hands 3a, minute hands 3b and second hands 3c, which are movable relative to hour markings 5 ​​on an hour circle 4. In the example shown, the dial 2 comprises an aperture 6 passing through the entire thickness of the dial 2, beneath which a date disc 7 moves.

[0032] In this respect, this manufacturing method comprises a providing step 20 in which a substrate for forming a watch component 2 is supplied. This providing step 20 may include a blanking sub-step 21 in which the substrate is blanked into a plate to the size of the watch component 2 to be manufactured; the plate may have a thickness suitable for the watch component 2. The plate and therefore the substrate are made of a material configured to withstand the enamel firing temperatures. These temperatures are preferably higher than 500 degrees Celsius, even between 700 and 1,300 degrees Celsius. As an example, the material may be a metal or a metal alloy, such as steel, or even a ceramic.

[0033] The material may also be transparent, for example single-crystal or polycrystalline materials such as quartz, spinel or corundum, in particular sapphire. Amorphous materials may also be used, for example mineral glass, provided that its softening point is above the enamel firing temperature.

[0034] Next, the method includes a preparation step 22 for preparing a colored enamel composition. This preparation step 22 then includes a production sub-step 23 for producing an enamel preparation. In particular, this can be a production sub-step 23 of a colorless, colored, translucent or transparent enamel preparation. This production sub-step 23 is carried out using an operation method and a preparation method well known in the prior art, which will not be described in detail herein, and the method can obtain a colorless, colored, translucent or transparent enamel preparation. It is particularly important to note that the enamel preparation is produced using a water-based or oil-based base mixed with enamel. In addition, the colorless or colored enamel preparation is also referred to as an "initial colorless or colored enamel composition".

[0035] Next, this preparation step 22 comprises a packaging sub-step 24, in which the colored pigments are encapsulated in a transparent protective shell of inorganic material, also called "transparent protective cover of inorganic material". This packaging sub-step 24 involves encapsulating each pigment to be used in the colored enamel composition in such a transparent protective shell, in particular in order to improve the thermal and / or chemical stability of the pigment. In fact, this improved thermal stability enables each encapsulated pigment to maintain its complete crystal structure when the temperature of the medium in which it is located is raised to the enamel firing temperature.

[0036] Such color pigments are preferably bright colors or even dazzling colors, such as red, yellow, orange, green, pink, and even blue and their variants. "Bright colors" refers to intense colors, which have an L* component greater than 40 in the CIELAB color space, measured in transmission mode under standard illuminant D65, an observer angle of 10°, and an optical geometry at d: 0° (in accordance with standards CIE No. 15, ISO 7724 / 1, DIN 5033 Teil 7, ASTM E-1164). It should be noted that CIELAB is the 1976 CIEL*a*b* color space, which is particularly used to characterize surface colors.

[0037] In this embodiment of the present invention, these color pigments are inorganic pigments. In particular, these pigments are non-toxic inorganic pigments. Such pigments belong to the (oxy)nitride family, the cerium sulfide family or even the phosphate family non-exhaustively and non-restrictively. It should be noted that the pigments from the (oxy)nitride family are generally bright colors, from red to green, from blue to yellow. As for the pigments belonging to the cerium sulfide family, they are basically bright colors, from red to orange. As for the pigments of the phosphate family, they have bright blue, green or even purple.

[0038] This encapsulation sub-step 24 involves a process of forming / applying a uniform and consistent layer of material on the entire surface of each pigment, the material being made of a metal oxide. To this end, the material is deposited on the surface at least once to form such a layer. In this respect, the layer thus forms a protective shell encapsulating each pigment. It will be appreciated that a cycle of depositing the material on the surface can be configured to obtain a given thickness of the layer. In fact, the thickness of the layer can vary according to the characteristics of the colorless enamel preparation to be applied to the watch component 2 and / or the characteristics of the colored enamel coating.

[0039] It will be appreciated that such a layer is of course transparent so as not to alter the inherent colour of the brightly coloured pigments.

[0040] In a non-limiting and non-exhaustive manner, the metal oxide constituting the uniform and consistent material layer may be the following: silicon dioxide with the chemical formula SiO2, aluminum oxide with the chemical formula Al2O3, zinc oxide with the chemical formula ZnO or even titanium oxide with the chemical formula TiO2.

[0041] This encapsulation sub-step 24 makes it possible, for example, to form this layer and accordingly a protective shell encapsulating each pigment using a technique for depositing at least one atomic layer (i.e. the well-known acronym ALD for “atomic layer deposition”). In the context of the present invention, this technique thus makes it possible to deposit a thin layer on the surface of each color pigment by means of a chain reaction in the gas phase using a metal oxide precursor, for example trimethylaluminum when the metal oxide is aluminum oxide.

[0042] In one embodiment, the layer encapsulating each pigment can be formed using microemulsion technology. This technology enables metal oxides to be deposited on the surface of the pigment by means of a microemulsion reaction using a precursor of the metal oxide. In the context of the present invention, when the metal oxide is silicon dioxide, the precursor can be tetraethyl orthosilicate.

[0043] In another variation, the layer encapsulating each pigment can be formed using a combination of these two techniques. For example, such formation can be, but is not limited to, starting with the use of the ALD technique and then using the microemulsion technique.

[0044] It will be appreciated that the encapsulation sub-step 24 is thus intended to encapsulate each pigment in a protective shell formed by a layer of transparent material included on the surface of the pigment. Such a layer is characterized by:

[0045] - its uniformity;

[0046] - its consistency;

[0047] - a thickness between 2 nm and 1,000 nm, preferably 10 nm, or preferably 30 nm, or more preferably 50 nm;

[0048] - its rigidity; and / or

[0049] - Its transparency.

[0050] It should also be noted that this layer and therefore the protective shell can simultaneously provide effective protection for the color pigments from:

[0051] - Oxidation at enamel firing temperatures;

[0052] - Attack by acidic media, especially pH Weakly acidic medium;

[0053] -Exposure to UV radiation;

[0054] -Erosion of cosmetics.

[0055] The step 22 of preparing the colored enamel composition further includes a mixing sub-step 25, in which the encapsulated colored pigment is mixed with the colorless enamel preparation. The mixing sub-step 25 is used to obtain the colored enamel composition, in which the encapsulated colored pigment is then dispersed. In the mixing sub-step 25, the obtained mixture corresponding to the colored enamel composition contains up to 30% by mass, or even up to 50% by mass of the encapsulated colored pigment.

[0056] This mass percentage may preferably be between 2% and 30%.

[0057] The mass percentage may preferably also be between 5% and 30%.

[0058] This mass percentage may preferably also be between 5% and 10%.

[0059] It will be appreciated that the mass percentages of the color pigments provide a compromise between color, transparency and color strength of the mixture while ensuring good final properties (eg mechanical properties, homogeneity, etc.).

[0060] It should also be noted that mixing can be performed by wet mixing or any other mixing method known to those skilled in the art.

[0061] Subsequently, the method comprises a treatment step 26 of treating said receiving zone 8 of the substrate to which the colored enamel coating is to be applied. In this treatment step 26, a degreasing agent and / or a bonding agent may be applied to the receiving zone 8 intended to contain the colored enamel coating 10.

[0062] Then, the method comprises an application step 27, in which at least one layer of the prepared colored enamel composition is applied to a receiving zone 8 of the substrate. It is understood that the receiving zone 8 may be, for example, all or part of the visible face 9 of the timepiece component 2 when it is mounted in the timepiece 1. In this application step 27, the layer of colored enamel composition may be deposited on the receiving zone 8 by spraying, spraying and / or printing.

[0063] Then, the method comprises a firing step 28, in which the at least one layer of colored enamel composition included in the substrate receiving area 8 is fired. In this firing step, the substrate is fired at a temperature between 300 and 1,200 degrees, preferably between 500 and 800 degrees, preferably at 690 degrees, with a residence time between 1 minute and 10 minutes, preferably 5 minutes. This firing step 28 is carried out in the open air or in a controlled atmosphere, for example under argon, nitrogen or vacuum.

[0064] It should be noted that this firing step 28 may involve a drying sub-step 29 in which the layer of colored enamel composition covering the receiving area 8 of the substrate is dried before firing. This drying sub-step 29 serves to eliminate any moisture present in the layer of colored enamel composition before firing. All common drying methods can be used, such as air drying, oven drying or radiation drying.

[0065] It should be noted that the sequence of application step 27 and firing step 28 of the method can be repeated, if necessary, in order to obtain a specific or desired thickness of the colored enamel coating on the receiving area 8 and on the timepiece component 2. In this respect, the thickness depends on the number of layers constituting the colored enamel coating 8. It will be understood that this thickness is defined specifically according to the characteristics of the colored enamel coating to be achieved on the timepiece component 2, in particular its aesthetic characteristics.

[0066] The method further comprises a final machining / finishing step 30 of final machining / finishing the substrate on a receiving area of ​​the substrate intended to receive the fired colored enamel composition layer, so as to obtain a timepiece component 2 comprising a colored enamel coating 10. Thus, the final machining / finishing step 30 may comprise a gem cutting sub-step 31 of cutting the substrate, in particular the fired colored enamel composition layer. The gem cutting sub-step 31 may be performed until the desired uniform thickness of the colored enamel coating 10 is obtained. The final machining / finishing step 30 then comprises a polishing or texturing sub-step 32 in which the substrate, in particular the fired colored enamel composition layer darkened during the gem cutting sub-step 31, is polished or texturized.

[0067] This final machining / finishing step 30 may also include a machining sub-step 33 in order, if necessary, to dimension the substrate in order to be mounted in timepiece 1 .

[0068] It should be noted that, when the timepiece component is a dial 2, a machining operation may be performed on this dial 2 to form a through opening through which the drive shafts of the hands 3a to 3c may be inserted. In this respect, the inlay / gradient creation operation may also be performed if it has not yet been completed. These inlays may be drawn, pressed or glued directly on the visible face, or even glued via a part that passes through the dial 2 by means of holes formed during the machining operation.

[0069] The above description relates to preferred embodiments, but should in no way be considered limiting, especially with regard to the type of color pigments used to color the enamel. In fact, other color pigments besides bright color pigments are also part of the present invention.

[0070] Technical terms

[0071] 1. Clocks

[0072] 2. Watch parts, such as dials

[0073] 3a.Hour hand

[0074] 3b.Minute hand

[0075] 3c. Second hand

[0076] 4. Hour Marking

[0077] 5. Time circle

[0078] 6. Hole

[0079] 7. Date dial

[0080] 8. Base and watch component receiving area

[0081] 9. Visible surfaces of watch parts

[0082] 10. Colored enamel coating

Claims

1. A method for producing a timepiece component (2) comprising a colored enamel coating (10), the method comprising the following steps: - a step of providing a substrate (20) selected from materials capable of withstanding the enamel firing temperature; - a preparation step (22) of a colored enamel composition constituting the colored enamel coating of the timepiece component (2), the preparation step (22) comprising a packaging sub-step (24) of packaging the colored pigment in a transparent protective shell made of an inorganic material and a mixing sub-step (25) of mixing the packaged colored pigment with an enamel preparation; - an application step (27) of applying at least one layer of the prepared colored enamel composition to the receiving area (8) on the substrate; - A firing step (28) of firing the layer of colored enamel composition included in the receiving area (8).

2. The method according to claim 1, characterized in that In the encapsulation sub-step, a process of forming a uniform and consistent material layer is applied to the entire surface of each color pigment, the material of the material layer being made of metal oxide.

3. The method according to claim 2, characterized in that The forming process is performed using the ALD technique and / or the microemulsification technique.

4. The method according to any one of claims 1 to 3, characterized in that The color enamel composition contains at most 30% by mass of encapsulated color pigments.

5. The method according to any one of claims 1 to 3, characterized in that The color enamel composition contains at most 50% by mass of encapsulated color pigments.

6. The method according to any one of the preceding claims, characterized in that The method comprises a treatment step (26) of treating the receiving area on the substrate to which the layer of colored enamel composition is applied, the treatment step (26) comprising applying a degreasing agent and / or a bonding agent to the receiving area.

7. The method according to any one of the preceding claims, characterized in that The method comprises a final machining / finishing step (30) of final machining / finishing the substrate in a receiving area (8) of the substrate for receiving a layer of colored enamel composition, the final machining / finishing step (30) comprising a gem cutting sub-step (31) and a polishing sub-step (32).

8. The method according to any one of the preceding claims, characterized in that Each color pigment is a bright color pigment.

9. The method according to any one of the preceding claims, characterized in that Each color pigment is an inorganic pigment or a non-toxic inorganic pigment.

10. A watch component (2), characterized in that: The timepiece component (2) is obtained using a method according to any one of the preceding claims.

11. The timepiece component (2) according to claim 10, characterized in that The timepiece component (2) comprises a substrate selected from materials configured to withstand enamel firing temperatures, a receiving area (8) on the substrate comprising a colored enamel coating containing encapsulated brightly colored inorganic non-toxic pigments.

12. The timepiece component (2) according to any one of claims 10 and 11, characterized in that The colored enamel coating forms a decorative element.

13. A timepiece (1), characterized in that: The timepiece (1) comprises a timepiece component (2) according to any one of claims 10 to 12.

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