Phosphorescent timepiece component

Abstract

The present invention relates to a watch component comprising a multilayer phosphorescent structure (3) comprising a front layer (1) with a transparent or translucent polymer matrix and comprising phosphorescent pigments and an underlying reflective layer (2).

Description

technical field

[0001] The invention relates to a multilayer phosphorescent watch component, in particular a watch strap. Technological background

[0002] The use of photoluminescent materials is quite widespread on the market for various applications, such as tires, signaling accessories, etc. (For example: US6431236B1, JPH10121424A).

[0003] Watchmaking companies offer phosphorescent silicone straps, and more recently, the market has expanded with a company offering a watch with a phosphorescent rubber strap. For its luminescent synthetic rubber strap, this company adds pigments directly to the material, which is then hot-molded and pressed.

[0004] However, when the pigment is dispersed throughout the material in this way, a significant proportion of the light it produces is lost, either through absorption in the case of thick layers, or through emission to the back surface, which is of no benefit to the wearer. As a result, a substantial proportion of expensive phosphorescent pigments are effectively wasted.

[0005] Document JPH07265111 describes a decorative element, for example, a pendant or keychain, consisting of a basic plastic or metal element with a defined shape. A reflective layer is formed on the surface of the basic element, and this layer is in turn covered with a photoluminescent layer. Summary of the invention

[0006] The invention aims to provide a phosphorescent structure that does not suffer from the disadvantages described above.

[0007] The present invention relates to a watch component according to the terms of the attached claim 1.

[0008] Preferably, the two layers of the structure of the invention comprise a polymeric matrix, advantageously elastomeric.

[0009] By elastomeric, we mean a material with a modulus of elasticity less than 100 MPa, preferably less than 50 MPa. Most preferably, the elastomer has a modulus of elasticity less than 10 MPa at 25°C.

[0010] Advantageously, both layers comprise compatible polymers. By compatible, we mean that these two layers adhere to each other without the use of an adhesive layer.

[0011] Preferably, the polymers of both layers comprise polymers of the same nature, differing essentially by the pigments and / or fillers dispersed therein.

[0012] Advantageously, the front layer has a thickness between 0.04 and 1mm.

[0013] Preferably, the back layer is made reflective by the dispersion of a white pigment such as, preferably, titanium oxide.

[0014] Advantageously, the phosphorescent pigment has a particle size, measured by sieving, of less than 30µm.

[0015] Preferably, the front layer comprises at least 20% by weight of the phosphorescent pigment. Brief description of the figures

[0016] There figure 1 represents a schematic view of a cross-section illustrating the phosphorescent multilayer structure of a watch component according to the invention. figure 2 represents a schematic view of a watch comprising a bracelet forming a watch component according to the invention. Figure references

[0017] 1. Phosphorescent layer 2. Reflective layer 3. Watch band 4. Watch Detailed description

[0018] The present invention relates to a watch component comprising a phosphorescent multilayer structure that maximizes the structure's luminous performance while minimizing the amount of phosphorescent pigments in the overall structure. This structure is particularly well-suited for manufacturing watch components intended for watch straps. It is understood that the watch component can also form other constituent elements of a wristwatch, such as a watch dial, hands, a bezel, or a watch case.

[0019] According to the invention, the multilayer structure comprises a front face, intended to be seen in normal use, and a back face intended, for example, to be in contact with the skin in the case of a watch strap.

[0020] According to the invention, the front face comprises a front layer 1 including a transparent or translucent elastomeric matrix containing a phosphorescent pigment. The thickness of this layer is optimized so that the light emitted by the deeper pigments is not excessively absorbed by the material between said deeper pigment and the surface. Depending on the optical characteristics of the polymer matrix of the layer, this layer has a thickness of between 30 µm and 1 mm.

[0021] According to an alternative embodiment that is not part of the invention, a thin transparent layer may optionally be added over the phosphorescent layer, provided that it does not significantly absorb the emitted light. Such an additional layer may, for example, be added to improve the surface finish of the final product or to protect the area containing the pigment.

[0022] Beneath the front layer is a reflective layer 2. This layer can be either a thin reflective layer, such as a thin metallic layer deposited, for example, by evaporation or plasma deposition onto a substrate, or, preferably, a polymer layer loaded with a reflective pigment, such as titanium oxide. This layer can also be deposited onto a substrate or be a self-supporting layer. This layer 2 can, for example, form the back layer 2 of the bracelet in contact with the skin, as shown in the diagram. figures 1 and 2 . However, the structure could include a third layer (not shown) for example coloured, for example placed above the front layer 1, the important thing to solve the aforementioned problem being that the layer immediately below the phosphorescent layer is reflective.

[0023] The small size of TiO₂ particles (typically between 200 nm and 400 nm) maximizes the reflection of visible light. The base mixture advantageously includes an elastomer, a vulcanization system, silica, titanium dioxide, and an optical brightener.

[0024] In order to exhibit sufficient reflection, the reflective layer, when of polymeric nature as described above, has a thickness of at least 20µm, preferably at least 40µm.

[0025] The front layer 1 and the reflective layer, when it is of polymeric nature, are preferably chosen from the set comprising a fluorinated elastomer of the FKM family or a thermoplastic elastomer polymer of the TPU (Polyurethanes), EVA (Ethylene vinyl acetate copolymer), silicones, EPR (ethylene propylene rubber) and their thermoplastic derivatives (TPO) family or of the acrylic elastomer family, or a mixture of the latter.

[0026] In the case of a watch strap, the total thickness of the back layer, beneath the phosphorescent layer, including the reflective layer 2 and any additional layer, is between 20µm and 1.5mm. Three shaping techniques are preferred for manufacturing watch straps: The lower layer can be overmolded onto the upper phosphorescent elastomer layer (or vice versa). The phosphorescent layer can be molded, and the reflective layer can be spray-coated. The two layers (produced separately by injection or compression) can be joined using a "saddle strap" forming technique: the two layers are glued and sewn together to form a strap. Example of a completed project.

[0027] A. Substrate preparation.

[0028] A fluoroelastomer is prepared by mixing a pure FKM Tecnoflon ®< P-457 grade from Slovay by working on an open mixer with 5% titanium oxide.

[0029] At the end of mixing a vulcanization system is added (2.5% by weight of Luperox ®< 101XL-45 + 3% by weight of Drimix ®< TAIC 75%, the percentages being expressed relative to the polymer).

[0030] Preferably, up to 1.8% of Nafol 1822B™ oil, marketed by Sasol, is also added. This mixture constitutes the FKM reflective blend, ready for shaping.

[0031] This mixture is shaped by compression and partially cross-linked.

[0032] B. Preparation of the phosphorescent layer

[0033] The following masterbatch is produced: Solvay's pure FKM Tecnoflon ®< P-457 grade, which is manufactured on a clean line and is transparent, is used as the matrix for the masterbatch.

[0034] Tecnoflon ®< P-457 is diluted in a 1:1 ratio in methyl ethyl ketone (Methyl Ether Ketone or MEK).

[0035] A photoluminescent pigment previously sieved to 30 µm is incorporated into the mixture obtained in the previous step, the quantity of pigment being in a ratio 1:1 with respect to Tecnoflon ®< P-457 and the whole is mixed on a high speed mixer at 3000 rpm-1.

[0036] A fluorochrome is introduced at a level of 0.5% relative to the total (i.e. 1.5% relative to the FKM polymer) and the whole is again mixed on a high-speed mixer at 3000 rpm-1.

[0037] The solvent is evaporated in an oven at 80°C until the solvent is eliminated.

[0038] The previously prepared master mix is ​​incorporated at a minimum rate of 60% into a pure FKM P-457 by working on an open mixer.

[0039] At the end of mixing a vulcanization system is added (2.5% by weight of Luperox ®< 101XL-45 + 3% by weight of Drimix ®< TAIC 75%, the percentages being expressed relative to the polymer).

[0040] Preferably, up to 1.8% of Nafol 1822B™ oil, commercially available from Sasol, is also added. This constitutes the optimized photoluminescent FKM mixture, ready for shaping and crosslinking.

[0041] The resulting mixture B is then overmolded by compression and crosslinked onto the previously prepared substrate A.

[0042] The resulting component comprises a 100µm front layer with a pigment concentration of 30% adhered to a reflective elastomer layer comprising 10% titanium oxide.

Claims

1. A horology component comprising a phosphorescent multilayer structure (3) comprising a front layer (1) with a transparent or translucent polymer matrix and comprising phosphorescent pigments and an underlying reflective layer (2) in which the front layer (1) comprises an elastomer matrix.

2. The horology component according to claim 1, in which the underlying layer (2) comprises a polymer matrix filled with a reflective pigment.

3. The horology component according to claim 2 in which the reflective pigment comprises titanium oxide.

4. The horology component according to claim 2 or 3, in which the polymer matrix of the underlying layer (2) is compatible with the polymer matrix of the front layer (1).

5. The horology component according to claim 4, in which the front layer (1) and the underlying layer (2) comprise a fluoroelastomer.

6. The horology component according to any of the preceding claims, in which the front layer (1) has a thickness comprised between 0.03 mm and 1 mm.

7. The horology component according to any of the preceding claims forming a watch bracelet (4), a watch dial, hands, a bezel or a watchcase.

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