METHOD FOR MANUFACTURING A ILLUMINATED CLOCK COMPONENT

Description

technical field

[0001] The invention relates to a method for manufacturing a luminescent watch component. Technological background

[0002] The use of photoluminescent materials is quite widespread on the market for various applications, such as hands or indices.

[0003] Phosphorescence technology is commonly used in watchmaking through various decorative methods to illuminate hands, dials, and other components. US patent 10 520 894 B2 describes a watch component composed of a polymer matrix incorporating phosphorescent and / or fluorescent pigments.

[0004] Fluorescence technology is also used for decorating internal watch components via pad printing or spraying using fluorescent pigments to decorate the watch in multiple colors.

[0005] On the other hand, the dials and hands are usually made of a metallic material and then, after several finishing stages, decorated with either phosphorescent or fluorescent ink.

[0006] This design has several drawbacks: the limitation of luminous performance, the thicknesses of phosphorescent and fluorescent inks are limited to a hundred microns with current decoration processes; a complexity of decoration processes, a white undercoat is indeed necessary before phosphorescent decoration in order to have an opaque decoration and maximize performance; completely opaque components limiting the design. Summary of the invention

[0007] The invention aims to provide a method for manufacturing a luminescent watch component that does not suffer from the disadvantages described above.

[0008] The present invention relates to a method for manufacturing a luminescent watch component for a wearable object, comprising the following steps: Mix an epoxy resin and a phosphorescent pigment at a ratio of 40% by mass; add a fluorescent pigment at a ratio of 3% by mass to the mixture; optionally, add silane to the mixture at a ratio of 10% by mass; add a hardener and mix everything mechanically to obtain a homogeneous solution; pour the resulting solution under vacuum into a mold and crosslink the solution to obtain a luminescent molded part; after hardening, remove the part from the mold and machine it to obtain the luminescent watch component.

[0009] According to other advantageous variants of the invention: The process includes an optional final step in which the watch component is decorated by printing or engraving; the resulting solution is poured into the mold to a thickness of at least 0.4 mm; the resin used is chosen from polyepoxide or polyurethane type resins; the resulting solution is crosslinked for 4 hours at 80°C; the hardener is based on acid anhydride, phenol, amine, diisocyanates or triisocyanates with polyols containing at least two hydroxyl groups; the luminescent watch component formed is a dial or a hand. Detailed description

[0010] The present invention relates to a method for manufacturing a luminescent watch component for a portable object.

[0011] By luminescent, we mean that the component is photoluminescent, fluorescent, phosphorescent, or a combination thereof.

[0012] Phosphorescent refers to an element that has the property of absorbing light and re-emitting it at a longer wavelength. This emission persists for a certain time after the light excitation has ceased. The ink contains at least one photoluminescent agent to impart photoluminescent properties. Preferably, the luminescent agent is a fluorescent agent. Advantageously, it is chosen from inorganic fluorophores and organolanthanide complexes. Alternatively, the fluorescent agent can also be chosen from organic fluorophores. Examples include fluorescein, europium 1,3-diphenyl-1,3-propanedionate-1,10-phenantroline, doped gadolinium oxysulfide, doped barium magnesium aluminate, doped lithium aluminate, doped strontium molybdate, and others.

[0013] Fluorescent materials are defined as elements that have the property of absorbing light and re-emitting it at a longer wavelength. Emission ceases when the light excitation ceases.

[0014] The various stages of the manufacturing process according to the invention will now be described.

[0015] In the first step, a resin and a phosphorescent pigment are mixed at a ratio of 40% by mass to obtain a sufficiently bright daytime color without compromising phosphorescent performance. The quantity of luminescent particles is chosen to be sufficient to make the decorated watch component stand out and be easily and immediately visible in the dark. Such pigments could, for example, be "Daylight Fluorescent Pigments" from Aralon Colors; other types of pigments can, of course, be used.

[0016] The resin used can be a polyepoxide or polyurethane type resin. Polyepoxide resins, commonly called "epoxy," are resins manufactured by polymerizing epoxy monomers with a hardener.

[0017] Next, a fluorescent pigment is added at a rate of 3% by mass, which modifies the visible color during the day because fluorescent pigments are colored. They also enhance and modify the phosphorescent effect. For example, if a blue-emitting phosphorescent pigment, "Light Blue," is used, and a pink fluorescent pigment is added, the final nighttime emission color will be pinkish / purple. It is therefore possible to match the visible color during the day with the visible color at night.

[0018] According to an optional embodiment of the invention, silane is added to the mixture at a maximum of 10% by mass to adjust the viscosity of the resin and thus make the deposition of the mixture in the mold faster and easier.

[0019] In the next step, a hardener is added and mechanical mixing is carried out, such as with a centrifugal planetary mixer of the "Speedmixer" type, to obtain a homogeneous solution and to distribute the luminescent particles well in the resin, thus avoiding clusters of particles which would impair both the visual appearance on the watch component and the performance of the luminescent ink.

[0020] The hardener can be based on acid anhydride, phenol, or amine. Polyurethane resins can also be used, by reacting di- or triisocyanates with polyols containing at least two hydroxyl groups.

[0021] The resulting homogeneous solution is then poured under vacuum into a mold. The solution is poured into the mold to a thickness of at least 0.4 mm, the thickness varying depending on the desired watch component. The inventors observed that below a thickness of 0.4 mm, the parts are too fragile and do not hold their shape mechanically (for example, a watch hand cannot support its own weight). Therefore, to guarantee good performance and durability, a minimum thickness of 0.4 mm is required.

[0022] There is no upper limit on thickness. It is possible to mold the part directly to the desired thickness and then cut it if it is flat. It is also possible to mold thicker parts and then machine them to achieve the same thickness. For example, this can be done with needles to allow for a wider needle shank and a thinner shank.

[0023] Once poured under vacuum, the homogeneous solution is crosslinked to obtain a luminescent molded part. The curing time and temperature will obviously vary depending on the resin chosen. Crosslinking can, for example, take place over 4 hours at a temperature of 80°C.

[0024] Naturally, the curing time and temperature depend on the technical specifications of the resin used. In this example, a curing time of 4 hours at 80°C corresponds to the parameters of the E2830 epoxy resin.

[0025] Finally, once the crosslinking is complete, the molded part is removed from the mold to perform laser cutting and obtain the luminescent watch component.

[0026] Finally, an optional last step involves decorating the resulting watch component by printing or engraving so that only a luminescent part of the component is visible.

[0027] According to the invention, such a process makes it possible to obtain a luminescent dial or hands. Example of a completed project.

[0028] An epoxy resin “E2830” manufactured by The Swatch Group R&D, Polymers Division is used.

[0029] A photoluminescent pigment is added to the E2830 resin at a rate of 40% by mass (particle size D50: 15-20 µm).

[0030] A fluorescent pigment is then added at a concentration of 3% by mass.

[0031] Silane (Dynasylan Glyeo from Evonik) can be added to this mixture at a maximum level of 10% by mass, to be adjusted according to the desired viscosity of the mixture.

[0032] The mixture is homogenized and then the hardener is added.

[0033] Mechanical mixing is carried out using a machine such as a centrifugal planetary mixer of the "Speedmixer" type in order to obtain a homogeneous solution.

[0034] The resulting mixture is then poured into a mold to a thickness of 0.4mm. The resin is then cured according to the conditions specified by the supplier (here for E2830 resin, 4 hours in an oven at 80°C).

[0035] Once the mold is removed, it is then laser-cut to obtain the desired watch parts.

Claims

1. Method for manufacturing a luminescent horological component for a portable object comprising the following steps: - mixing an epoxy resin and a phosphorescent pigment in an amount of 40% by mass; - adding to the mixture a fluorescent pigment in an amount of 3% by mass; - optionally, adding silane to the mixture in an amount of 10% by mass; - adding a hardener and mixing everything mechanically to obtain a homogenous solution; - pouring under vacuum the solution obtained into a mould and cross-linking the solution to obtain a luminescent moulded part; - after hardening, removing the part from the mould and blanking it by laser to obtain the luminescent horological component.

2. Manufacturing method according to claim 1, comprising a last optional step during which the horological component is decorated by printing or etching.

3. Manufacturing method according to claim 1 or 2, wherein the solution obtained is poured into the mould over a thickness of at least 0.4mm.

4. Manufacturing method according to claims 1 to 3, wherein the resin used is chosen from the resins of the polyepoxide type or of the polyurethane type.

5. Manufacturing method according to claims 1 to 4, wherein the solution obtained is cross-linked for 4 hours at 80°C.

6. Manufacturing method according to claims 1 to 5, wherein the hardener contains acid anhydride, phenol, amine, diisocyanates or triisocyanates with polyols containing at least two hydroxyl groups.

7. Manufacturing method according to claims 1 to 5, wherein the luminescent horological component formed is a dial or a hand.