Method of manufacturing a luminescent timepiece component

Abstract

The invention relates to a method of manufacturing a luminescent watch component for a portable object, comprising the following steps: mixing an epoxy resin and phosphorescent pigments in an amount of 40% by mass; adding fluorescent pigments to the mixture in an amount of 3% by mass; optionally, adding silane to the mixture in an amount of 10% by mass; adding a hardener and mechanically mixing all the materials to obtain a homogeneous solution; pouring the resulting solution under vacuum into a mold and cross-linking the solution to obtain a luminescent molded part; after hardening, removing the part from the mold and punching it by means of a laser to obtain a luminescent watch component.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method of manufacturing a luminescent watch component. The present invention also relates to such a watch component obtained using said manufacturing method. BACKGROUND

[0002] The use of photoluminescent materials is quite widespread on the market, for various uses, such as pointers or scales.

[0003] Photoluminescent technology is conventionally used in the watchmaking field through various decoration methods to illuminate pointers, dials and other components.

[0004] Fluorescent technology is also used for the decoration of internal case components to decorate watches with several colors, by using pad printing or spraying with fluorescent pigments.

[0005] Furthermore, dials and pointers are generally made of metal material and then decorated with phosphorescent or fluorescent ink after several termination steps.

[0006] This design has several drawbacks:

[0007] - limitation of the luminescent performance, the thickness of the phosphorescent and fluorescent ink being limited to about 100 microns for the current decoration methods;

[0008] - complication of the decoration method, a white base layer is indeed necessary before the phosphorescent decoration to have an opaque decoration and maximize the performance;

[0009] - limitation of the design with totally opaque components. SUMMARY

[0010] The present invention aims at providing a method of manufacturing a luminescent watch component without the above-mentioned drawbacks.

[0011] The present invention relates to a method of manufacturing a luminescent watch component for a portable item, comprising the following steps:

[0012] - mixing an epoxy resin and phosphorescent pigments in an amount of 40% by mass;

[0013] - adding fluorescent pigments to said mixture in an amount of 3% by mass;

[0014] - optionally, adding silane to said mixture in an amount of 10% by mass;

[0015] - adding a hardener and mechanically mixing all the materials to obtain a homogeneous solution;

[0016] - pouring the resulting solution under vacuum into a mold and cross-linking said solution to obtain a luminescent molded part;

[0017] - after hardening, the part is removed from the mould and machined to obtain a luminescent watch component.

[0018] According to other advantageous alternatives of the application:

[0019] - the method comprises a last optional step during which the watch component is decorated by printing or etching;

[0020] - the resulting solution is poured into a mould with a thickness of at least 0.4 mm;

[0021] - the resin used is chosen from resins of the polyepoxide type or resins of the polyurethane type;

[0022] - the resulting solution is crosslinked at 80°C for 4 hours;

[0023] - the hardener contains an acid anhydride, a phenol, an amine, a di- or tri- isocyanate and a polyol containing at least two hydroxyl groups;

[0024] - the luminescent watch component formed is a dial or a hand.

[0025] The application also relates to a luminescent watch component obtained using such a method.

[0026] The application also relates to a watch comprising at least one such watch component. DETAILED DESCRIPTION

[0027] The application relates to a method for manufacturing a luminescent watch component for a portable item, and to the luminescent watch component obtained.

[0028] Luminescence means that the component is photoluminescent, fluorescent, phosphorescent or a combination thereof.

[0029] Phosphorescence means that the element has the property of being able to absorb light and re-emit it at a greater wavelength. This emission lasts for a period of time when the photoexcitation stops. The ink contains at least one luminescent agent to impart photoluminescent properties to the ink. Preferably, the luminescent agent is a fluorescent agent. It is advantageously chosen from inorganic fluorophores and organic-lanthanide complexes. According to another alternative, the fluorescent agent can also be chosen from organic fluorophores. This can be, for example, fluorescein, 1,3-diphenyl-l,3-propanedioic acid- 1,10-phenanthroline europium, gadolinium oxysulfide-doped, barium magnesium aluminate-doped, lithium aluminate-doped, strontium molybdate-doped.

[0030] Fluorescence means that the element has the property of being able to absorb light and re-emit it at a greater wavelength. This emission stops when the photoexcitation stops.

[0031] The various steps of the manufacturing method according to the application are now described.

[0032] During the first step, a mixing of the resin and phosphorescent pigments in an amount of 40% by mass is carried out to obtain a daytime color that is sufficiently visible without any compromise on the phosphorescent performance. The amount of luminescent particles is chosen to be sufficient to make the decorated watch component visible and to make it easily and immediately visible in the dark. Such pigments can be, for example, the Daylight Fluorescent Pigments from Aralon Colors, other types of pigments can of course be used.

[0033] The resin used can be a polyepoxide or polyurethane type resin. Polyepoxide resins, commonly referred to as "epoxy resins", are resins made by polymerization of epoxide monomers using a hardener.

[0034] Then fluorescent pigments are added in an amount of 3% by mass, which is able to change the daytime visible color since fluorescent pigments are colored. They are also able to enhance and change the phosphorescent effect. For example, if a "Light Blue" blue emitting phosphorescent pigment is used and pink fluorescent pigments are added, the final emitted color at night is pink / purple. It is thus possible to have the daytime visible color correspond to the nighttime visible color.

[0035] According to an optional embodiment of the application, silane is added to the mixture in an amount of at most 10% by mass to adjust the viscosity of the resin and thus make the deposition of the mixture in the mold faster and easier.

[0036] During the next step, a hardener is added and mechanical mixing is carried out by means of a centrifugal planetary mixer of the Speedmixer type to obtain a homogeneous solution and to distribute the luminescent particles sufficiently in the resin, thus avoiding particle clusters that have a negative impact on both the visual finish on the watch component and the performance of the luminescent ink.

[0037] The hardener can contain an acid anhydride, a phenol or an amine. Polyurethane resins can also be used by reacting a di- or tri-isocyanate with a polyol containing at least two hydroxyl groups.

[0038] The resulting homogeneous solution is then poured into a mold under vacuum. The resulting solution is poured into the mold in a thickness of at least 0.4 mm, this thickness being different according to the watch component that is finally to be obtained. The inventors point out that below a thickness of 0.4 mm, the component is too fragile and lacks mechanical support (for example a hand cannot support its own weight). Thus, to ensure good performance and good strength, a minimum thickness of 0.4 mm is required.

[0039] There is no upper limit to the thickness. If the part is flat, the part can be made directly with the thickness and blanked. It is also possible to mold thicker parts and machine them to modify them in terms of thickness. For example, for a hand, to be able to blank it, the top of the hand is made wider and the stem thinner.

[0040] Once molded under vacuum, the homogeneous solution is cross-linked to obtain a luminescent molded piece. The time and temperature of cross-linking of course vary according to the chosen resin. The cross-linking can be carried out for example at a temperature of 80°C for 4 hours.

[0041] Of course, the time and temperature of cross-linking depend on the technical specifications of the resin used. In the present example, a cross-linking time of 4 hours at 80°C corresponds to the parameters of the epoxy resin E2830.

[0042] Finally, once the cross-linking is complete, the molded piece is removed from the mold to be laser-blanked and to obtain a luminescent watch component.

[0043] Finally, the last optional step consists in decorating the resulting watch component by printing or etching so that only the luminescent part of the component is visible.

[0044] According to the application, this process makes it possible to obtain a luminescent dial or hand.

[0045] Embodiment

[0046] The "E2830" epoxy resin manufactured by The Swatch Group R&D, Polymer Division is used.

[0047] The photoluminescent pigments are added to the E2830 resin in a quantity of 40% by mass (particle size D50: 15-20 pm).

[0048] The fluorescent pigments are then added in a quantity of 3% by mass.

[0049] The silane (Dynasylan Glyeo from Evonik) is added to this mixture in a maximum quantity of 10% by mass, this quantity being adjusted according to the desired viscosity of the mixture.

[0050] The mixture is homogenized and then the hardener is added.

[0051] Mechanical mixing is carried out using a machine of the Speedmixer type, centrifugal planetary mixer type, to obtain a homogeneous solution.

[0052] The mixture thus obtained is then poured into a mold to have a thickness of 0.4 mm. The resin is then cross-linked according to the conditions specified by the supplier (here for the E2830 resin, 4 hours at 80°C in an oven).

[0053] Once the shaped body is removed from the mould, it is subsequently punched by means of a laser to obtain the required watch component.

Claims

1. Process for manufacturing a luminescent watch component for a portable object, comprising the following steps: - mixing an epoxy resin and phosphorescent pigments in an amount of 40% by mass, to obtain a mixture; - adding to the mixture fluorescent pigments in an amount of 3% by mass; - optionally, adding silane to the mixture in an amount of 10% by mass; - adding a hardener and mechanically mixing all the materials to obtain a homogeneous solution; - pouring the resulting solution under vacuum into a mould at a thickness of at least 0.4 mm and cross-linking the solution to obtain a luminescent moulded part; - after hardening, removing the part from the mould and punching it by means of a laser to obtain a luminescent watch component, wherein the luminescent watch component formed is a pointer, and wherein the fluorescent pigments are blue-emitting phosphorescent pigments to which pink fluorescent pigments are added.

2. Manufacturing process according to Claim 1, comprising a last optional step during which the watch component is decorated by printing or etching.

3. Manufacturing process according to Claim 1 or 2, wherein the resulting solution is cross-linked at 80°C for 4 hours.

4. Manufacturing process according to one of Claims 1 to 3, wherein the hardener contains an acid anhydride, a phenol or an amine.

5. Luminescent watch component obtained by the process according to one of Claims 1 to 4.