CH718148A2 - Phosphorescent watch component. - Google Patents

Abstract

The present invention relates to a watch 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 reflecting layer (2).

Description

Technical area

The invention relates to a multilayer phosphorescent watch component, in particular a watch strap.

Technology background

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

[0003] Watchmaking companies in particular offer silicone-based phosphorescent bracelets, and more recently the offer has been developed via a company offering a watch equipped with a phosphorescent rubber bracelet. For its luminescent synthetic rubber strap, this company adds pigments directly into the material, which is then heat molded and pressed.

[0004] Nevertheless, when the pigment is thus dispersed in the mass, a significant proportion of the light produced by the pigments is lost, either by absorption in the material in the case of thick layers, or by emission towards the rear face which does not represents no interest for the bearer. In this way, a significant proportion of the expensive phosphorescent pigments is practically unused.

Summary of the invention

The invention aims to provide a phosphorescent structure which does not suffer from the drawbacks described above.

The present invention relates to a watch component comprising a phosphorescent structure comprising a transparent or translucent front layer and comprising phosphorescent pigments and an underlying reflective layer.

Preferably, the two layers of the structure of the invention comprise a polymer matrix, advantageously elastomeric.

[0008] By elastomeric, we mean a material having a modulus of elasticity of less than 100 MPa, preferably less than 50 MPa. Particularly preferably, the elastomer has an elastic modulus of less than 10 MPa at 25°C.

[0009] Advantageously, the two layers comprise compatible polymers. By compatible, we mean that these two layers adhere to each other without the use of an adhesive layer.

[0010] Preferably, the polymers of the two layers comprise polymers of the same nature, differing essentially by the pigments and/or the fillers which are dispersed therein.

[0011] Advantageously, the front layer has a thickness of between 0.04 and 1 mm.

[0012] Preferably, the rear layer is made reflective by the dispersion of a white pigment such as, preferably, titanium oxide.

[0013] Advantageously, the phosphorescent pigment has a particle size, measured by sieving, of less than 30 μm.

[0014] Preferably, the front layer comprises at least 20% by weight of the phosphorescent pigment.

Brief description of figures

[0015] FIG. 1 represents a schematic view of a section illustrating the phosphorescent multilayer structure of a timepiece component according to the invention. FIG. 2 represents a schematic view of a watch comprising a bracelet forming a timepiece component according to the invention.

Figure references

[0016] 1. Phosphorescent layer 2. Reflective layer 3. Watch strap 4. Watch

detailed description

The present invention relates to a watch component comprising a phosphorescent multilayer structure making it possible to maximize the light performance of the structure while minimizing the quantity of phosphorescent pigments in the complete structure. This structure is particularly suited to the manufacture of watch components intended to produce watch straps. It goes without saying that the timepiece component can also form other constituent elements of a wristwatch such as a watch dial, hands or even a bezel or a watch case.

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

According to the invention, the front face comprises a transparent or translucent polymeric front layer 1 comprising a phosphorescent pigment. The thickness of this layer is optimized so that the light emitted by the deepest pigments is not excessively absorbed by the material comprised between said deep 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.

[0020] A thin transparent layer can optionally be added over the phosphorescent layer, provided that it does not significantly absorb the light emitted. Such an additional layer can for example be added to improve the surface condition of the final product or to protect the zone comprising the pigment.

[0021] Under the front layer is arranged a reflective layer 2. This layer can either be a thin reflective layer such as a thin metallic layer deposited for example by evaporation or plasma deposition on a substrate, or, preferably, a layer of polymer charged with a reflective pigment such as, for example, titanium oxide. This layer can also be deposited on a substrate or even 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 Figures 1 and 2. However, the structure could include a third layer (not shown) for example colored, for example arranged at the above the front layer 1, the important thing to solve the aforementioned problem being that the layer immediately under the phosphorescent layer is reflective.

[0022] The small size of the TiO2 particles (typically between 200 nm and 400 nm) makes it possible to maximize the reflection of visible light. The base mixture advantageously comprises an elastomer, a vulcanization system, silica, titanium oxide and an optical brightener.

[0023] In order to present sufficient reflection, the reflective layer, when it is of a polymeric nature as described above, has a thickness of at least 20 μm, preferably of at least 40 μm.

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

[0025] In the case of a watch strap, the total thickness of the rear layer, under the phosphorescent layer, therefore comprising the reflective layer 2 and any additional layer has a thickness of between 20 μm and 1.5 mm.

Three shaping techniques are preferred for making bracelets: The lower layer can be overmolded on the upper layer of phosphorescent elastomer (or vice versa) The phosphor layer can be molded and the reflective layer can be spray coated. The two layers (produced separately by injection or compression) can be assembled using the shaping technique of the “saddle strap” type: the two layers are glued and sewn together to form a strap.

Example of realization.

A. Preparation of the substrate.

[0027] A fluoroelastomer is prepared by mixing a pure Tecnoflon<®>P-457 FKM grade from Slovay by working on an open mixer with 5% titanium oxide.

At the end of the mixture, 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).

[0029] Preferably, Nafol 1822B™ oil marketed by Sasol (up to 1.8%) is also added. The whole is the reflective FKM mixture ready to be shaped.

This mixture is shaped by compression and partially crosslinked.

B. Preparation of the phosphorescent layer

[0031] The following masterbatch is made: Solvay's pure Tecnoflon<®>P-457 grade FKM which is manufactured on a clean line and which is transparent is used as the matrix of the masterbatch. Tecnoflon<®>P-457 is diluted in a 1:1 ratio in methyl ethyl ketone (Methyl Ether Ketone or MEK). A photoluminescent pigment previously sieved at 30 µm is incorporated into the mixture obtained in the previous step, the quantity of pigment being in a 1:1 ratio with respect to the Tecnoflon<®>P-457 and the whole is mixed on a mixer high speed at 3000 rpm. A fluorochrome is introduced at 0.5% relative to the total (ie 1.5% relative to the FKM polymer) and the whole is again mixed on a high-speed mixer at 3000 rpm. The solvent is evaporated in an oven at 80° C. until elimination of the solvent. The masterbatch prepared beforehand is incorporated up to a minimum of 60% in a pure FKM P-457 by working on an open mixer. 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). Preferably, Nafol 1822B™ oil marketed by Sasol (up to 1.8%) is also added. The whole constitutes the optimized photoluminescent FKM mixture, ready to be shaped and crosslinked. The mixture B obtained is then overmoulded by compression and crosslinked on the substrate A previously prepared. The component thus obtained comprises a front layer of 100 μm having a pigment concentration of 30% adherent to a reflective elastomer layer comprising 10% titanium oxide.

Claims (8)

1. Watch 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). 2. Watch component according to claim 1 wherein the front layer (1) comprises an elastomer matrix. 3. Watch component according to claim 1 or 2 wherein the underlying layer (2) comprises a polymeric matrix filled with a reflective pigment. 4. Watch component according to claim 3, in which the reflective pigment comprises titanium oxide. 5. Timepiece component according to claim 3 or 4 wherein the polymer matrix of the underlying layer (2) is compatible with the polymer matrix of the front layer (1). 6. Watch component according to claim 5 wherein the front layer (1) and the underlying layer (2) comprise a fluoroelastomer. 7. Watch component according to one of the preceding claims, in which the front layer (1) has a thickness of between 0.03 mm and 1 mm. 8. Watch component according to one of the preceding claims forming a watch strap (4), a watch dial, hands, a bezel or a watch case.