CH719097A2 - Process for manufacturing a luminescent watch component. - Google Patents

Abstract

The present invention relates to a process for manufacturing a luminescent watch component, in particular a dial or a hand, comprising the steps of pre-mixing phosphorescent and fluorescent pigments with a plasticizer, mixing with a polymer base followed by a first extrusion , second extrusion to form a strip and its cutting. The band can optionally come with a white lower part.

Description

Technical field of the invention

The invention relates to a method of manufacturing a luminescent watch component. The present invention also relates to such a timepiece component obtained from the manufacturing process.

Technology background

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

[0003] Phosphorescence technology is commonly used in the field of watchmaking via various decoration methods in order to illuminate hands, dials and other components.

[0004] Fluorescence technology is also used for the decoration of internal trim components via pad printing or spraying using fluorescent pigments in order to decorate the watch and this in several colors.

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

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

Summary of the invention

The invention aims to provide a method of manufacturing a luminescent watch component which does not suffer from the drawbacks described above.

The present invention relates to a method of manufacturing a luminescent timepiece component for a portable object comprising the following steps: make a premix of a phosphorescent pigment at a height of 10 to 40% by mass, a fluorescent pigment at a height of 1 to 4% by mass and a plasticizer at a maximum height of 10% by mass, mixing a polymer base with said premix and extruding the mixture obtained for the first time to obtain a homogeneous polymer mixture; extruding the polymer mixture a second time to form a strip with a thickness of at least 0.3mm; cutting the strip to obtain the desired luminescent timepiece component;

[0009] In accordance with other advantageous variants of the invention: the polymer base is a thermoplastic polymer base; the polymer base is transparent to wavelengths of the near ultraviolet spectrum and to wavelengths of the visible spectrum; the thermoplastic polymer base is chosen from polycarbonate, PMMA, .... the extruded strip is cooled to ambient temperature; the first extrusion is carried out via a twin-screw extruder; the second extrusion is carried out via a single-screw extruder; the strip obtained during the second extrusion is in the form of a strip in two parts, a first part, called the upper part, is formed by the luminescent mixture obtained at the end of the first extrusion, and the second part, called the lower part, is formed by a strip of white polymer material.

The invention also relates to a luminescent timepiece component obtained from such a process.

[0011] The invention also relates to a timepiece comprising at least one such timepiece component.

Detailed description of the invention

The present invention relates to a method of manufacturing a luminescent timepiece component for a portable object, as well as the luminescent timepiece component obtained.

[0013] By luminescent, it is meant that the component is photoluminescent, fluorescent, phosphorescent, or a combination.

By phosphorescent is meant an element having the property of being able to absorb light and to re-emit it at a longer wavelength. The emission persists for a certain time when the light excitation has ceased. The ink contains at least one photoluminescent agent to impart photoluminescence properties to the ink. Preferably, the luminescent agent is a fluorescent agent. It is advantageously chosen from inorganic fluorophores and organo-lanthanide complexes. According to another alternative, the fluorescent agent can also be chosen from organic fluorophores. It may be, for example, fluorescein, europium 1,3-diphenyl-1,3-propanedionate-1,10-phenanthroline, doped gadolinium oxysulfide, doped barium and magnesium aluminate, d doped lithium aluminate, doped strontium molybdate.

[0015] Fluorescent means an element having the property of being able to absorb light and to re-emit it at a longer wavelength. The emission ceases when the light excitation ceases.

The various steps of the manufacturing process according to the invention will now be described.

During a first step, a pre-mixture of a phosphorescent pigment at 10 to 40% by mass, a plasticizer and a fluorescent pigment at 4% by mass is carried out so as to obtain a bright enough daytime color without compromising on glow-in-the-dark performance. The quantity of luminescent particles is chosen so as to be sufficient to be able to distinguish the decorated timepiece component and to make it easily and immediately visible in the dark. The plasticizers are present at a maximum height of 10% by weight to adjust the malleability of the polymer base thereafter and thus make it less brittle during handling and machining. This premixing makes it possible to coat the pigments, to avoid their abrasion and to facilitate their incorporation into the polymer base for the rest of the process. Polyethylenes, paraffins, or even polydimethoxysilanes are commonly used as plasticizers.

[0018] The daytime fluorescent pigment is added at a level of 1 to 4% by weight, which makes it possible to modify the daytime visible color because these fluorescent pigments are colored. Daylight fluorescent pigments are the equivalent of „Daylight fluorescent pigment“, these pigments have a daytime color unlike „UV Light fluorescent pigment“ which are color neutral under daylight but excited by UV light. They also make it possible to reinforce and modify the phosphorescent effect via an energy conversion. For example, if a blue emission phosphorescent pigment "Light Blue" is used, and pink fluorescent pigment is added, then the final night emission color will be pink/purple It is therefore possible, depending on the mixtures made, to make match the fluorescent color visible by day with the phosphorescent color visible by night.

During the next step, a mixture is carried out with the premix and a polymer base, then a first extrusion of the premix to obtain a homogeneous mixture and well distribute the luminescent particles in the polymer base and thus avoid clusters of particles which would harm both the visual rendering on the watch component and the performance of the luminescent pigments. The base polymer is thus mixed with the premix based on plasticizer and pigments in order to be able to allow sliding between the chains

The polymer base used can be a thermoplastic polymer such as polycarbonate (PC), polyamide (PA), Methylmethacrylate Acrylonitrile Butadiene Styrene (MABS), glycolized polyethylene terephthalate (PETg), etc. Advantageously, the polymer base used is both transparent to wavelengths of the near ultraviolet spectrum and to wavelengths of the visible spectrum, this allows better absorption of light by the pigments.

[0021] Preferably, the extrusion is carried out using a twin-screw extruder so as to obtain a homogeneous mixture and good dispersion of the pigments. At the end of this first extrusion, the material generally comes out in the form of granules, which facilitates transport and storage for the rest of the process.

The material obtained during the first extrusion is then re-extruded on a single-screw extrusion machine equipped with a die allowing the production of calendered strips with a thickness of at least 0.3 mm. The thickness can of course vary depending on the watchmaking component that one wishes to obtain at the end. It has been observed by the inventors that below a thickness of 0.3 mm, the parts are too fragile and do not hold together mechanically. For example, a 0.15 mm needle is too flexible and has inhomogeneous mechanical performance, the needle does not not supporting its own weight. Thus, in order to guarantee good performance and good hold, a minimum thickness of 0.3 mm is desired.

According to a variant of the invention, the profile obtained during the second extrusion is in the form of a strip in two parts, a first so-called upper part is formed by the mixture obtained at the end of the first extrusion, and the second part, called the lower part, is formed by a strip of white polymer material. Such an arrangement makes it possible to obtain a reflective layer under the layer of luminescent material and thus to obtain better performance.

[0024] There is no upper thickness limitation. It is possible to directly determine the thickness of the part and to cut the part if the latter is flat. It is also possible to extrude thicker strips and to machine the parts after cutting to also take them back in thickness. For example, for needles to be able to cut the top of the needle wider and a thinner foot. For cost reasons, the die can be adapted to the section of the largest needle in order to extrude the profile thereof.

[0025] Once the compound has been re-extruded, the strip is cut, via stamping or laser cutting for example, to obtain the desired luminescent watch component.

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

According to the invention, such a method makes it possible to obtain a luminescent dial or hands.

Example of realization

A premix is carried out by mixing a plasticizer at a maximum height of 10% by mass with a photoluminescent pigment at a height of 10 to 40% by mass (particle size D50: 15-20 μm) and a fluorescent pigment is then added at a level of 1 to 4% by mass. The plasticizing agent makes it possible to improve the solidity of the material, and to optimize the interactions matrix-phosphorescent pigment.

[0029] A polymer base is then mixed into the premix.

The mixture is homogenized via a first twin-screw extrusion.

A second extrusion of the compound is then carried out to form a strip with a thickness of at least 0.3 mm.

[0032] Cooling of the strip to room temperature.

[0033] Once the band has been formed and cooled, it is cut by laser or stamping in order to obtain the desired timepieces.

Claims (10)

1. Method for manufacturing a luminescent timepiece component for a portable object comprising the following steps: – make a premix of a phosphorescent pigment at 10 to 40% by weight, a fluorescent pigment at 1 to 4% by weight and a plasticizer at a maximum height of 10% by weight; – mixing a polymer base with said premix and extruding the mixture obtained for the first time to obtain a homogeneous polymer mixture; – extruding the polymer mixture a second time to form a strip of a predetermined thickness; – cut the strip to obtain the desired luminescent watch component. 2. Manufacturing process according to claim 1, characterized in that the polymer base is a thermoplastic polymer base. 3. Manufacturing process according to claim 1 or 2, characterized in that the polymer base is transparent to the wavelengths of the near ultraviolet spectrum and to the wavelengths of the visible spectrum. 4. Manufacturing process according to claims 1 to 3, wherein the thermoplastic polymer base is chosen from polycarbonate, PMMA. 5. Manufacturing process according to claims 1 to 4, wherein the extruded strip is cooled to room temperature. 6. Manufacturing process according to claims 1 to 5, wherein the first extrusion is carried out via a twin-screw extruder. 7. Manufacturing process according to claims 1 to 6, in which the second extrusion is carried out via a single-screw extruder. 8. Manufacturing process according to claims 1 to 6, in which the band obtained during the second extrusion is in the form of a band in two parts, a first so-called upper part is formed by the luminescent mixture obtained at the end of the first extrusion, and the second part, called the lower part, is formed by a strip of white polymer material. 9. Manufacturing process according to claims 1 to 8, in which the luminescent horological component formed is a dial or a needle. 10. Luminescent watch component obtained via a method according to one of claims 1 to 8.