Improved method for manufacturing a timepiece component

Abstract

The invention relates to a method for manufacturing a timepiece component (1) forming all or part of the exterior parts (6) of a timepiece or all or part of a timepiece movement (4), said method comprising a step of depositing droplets of a fluid (12A) by electrohydrodynamic inkjet printing so as to form at least one decoration of the timepiece component (1).

Description

IMPROVED MANUFACTURING METHOD FOR A CLOCK PART TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a method for manufacturing a watch part and in particular such a method comprising a step of depositing drops of a fluid onto a surface of the watch part. TECHNICAL BACKGROUND OF THE INVENTION

[0002] To create a decorative design on a watch component, for example, pad printing is commonly used. This involves using a pad to transfer an ink pattern onto the component. A typical example is printing graduations on a dial. Pad printing is very precise and reproducible, resulting in a highly prized aesthetic in watchmaking. However, it requires a separate tool for each design, which can make pad printing less cost-effective for small production runs. Furthermore, if multiple colors are needed, more tooling is required.

[0003] Inkjet printing of watch parts has already been attempted for small production runs that are difficult to make profitable with pad printing. However, the print heads currently available produce droplets with a diameter greater than 25 µm, which is incompatible with the advantageous aesthetics of pad printing. Indeed, curved lines are not sharp and exhibit a pixelated effect unsuitable for a high-quality timepiece. Furthermore, only relatively low viscosity is compatible with such a print head, limiting the types of fluid that can be used. Finally, the gloss and uneven surface finish (orange peel texture) are significantly less refined than with pad printing. SUMMARY OF THE INVENTION

[0004] The invention aims to propose a new type of manufacturing of a watch part comprising a deposition step which offers a precision and a result equivalent or even superior to pad printing while limiting the investment required regardless of the number of parts to be manufactured, the number of different fluids to be deposited or the nature of the fluid to be deposited.

[0005] To this end, the invention relates to a method for manufacturing a watch component forming all or part of a watch case or a watch movement, characterized in that it comprises the following steps: - obtain a rough draft of the watch part to be decorated; - deposit a coating on at least part of the blank using an electrohydrodynamic type inkjet droplet fluid intended to form at least one decoration on the watch part.

[0006] Advantageously, the process according to the invention uses an electrohydrodynamic inkjet deposition system that allows for versatile deposition on demand (continuous, semi-continuous, spot, etc.) and with a variety of fluid types (metallic, aqueous, polymer, ceramic, adhesive, oil, epilame) with ideal precision for watchmaking applications. Typically, the same type of watch component, using the same tooling, can be used to mass-produce a virtually unlimited number of different deposits on each component.Thus, depending on the type of fluid present on each ejection nozzle, a first part can receive a first deposition pattern with a first type of fluid, a second part of the same type can receive a second deposition pattern with the first type of fluid, a third part of the same type can receive the first deposition pattern with a second type of fluid, a fourth part of the same type can receive the first deposition pattern with the first type of fluid and the second deposition pattern with the second type of fluid, etc., without each part being much more expensive to produce than another.

[0007] Furthermore, an electrohydrodynamic nozzle uses a simple potential difference to eject a droplet much smaller than the fluid meniscus at the nozzle outlet. By selectively controlling the potential difference, it is therefore very easy to parameterize the frequency and timing of droplet ejection, with a dimension (diameter or height) approximately ten times smaller than with known ejection heads such as the piezoelectric type. This results in a coating that becomes compatible with watchmaking in general, offering resolution and rendering at least equivalent to those of pad printing, without the limitations in terms of production costs and fluids.

[0008] Finally, any type of timepiece can advantageously incorporate, on all or part of its external surface, the coating thus formed by a droplet deposition according to the invention. It is understood in particular that a wide variety of fluids deposited as droplets – the material of the timepiece – can be considered to form the decorative coating without being limited to printing solely by electrohydrodynamic inkjet printing, that is to say, in particular combined with another type of printing, while maintaining a result at least equivalent to pad printing, with the advantage of being able, for example, to personalize a timepiece on demand (word, signature, designs, etc.).), but also combined applications that are both technical and aesthetic, such as lubrication, bonding, metallization, or more generally, a selective deposition of a very precise coating that is not necessarily intended to be visible on the final application of the timepiece, such as, for example, to form an authentication pattern that is not visible to the naked eye without magnification and / or special illumination.

[0009] The invention may also include one or more of the following optional features, taken alone or in combination.

[0010] At least one decoration on the timepiece can be created solely by depositing the coating using a droplet fluid via an electrohydrodynamic inkjet process. This achieves optimal resolution for each decoration and allows for a wide variety of colors with a higher quality finish than pad printing or conventional inkjet printing (such as piezoelectric or thermal inkjet).

[0011] The deposition step can form a coating with a thickness (vertical direction) of less than 5 µm. Advantageously, according to the invention, the coating can be very thin. Indeed, depending on the desired aesthetic effect, it may be desirable for some of the incident light to be transmitted (partial transparency) through the coating to partially reflect the color of the area beneath the coating, thus creating a particular aesthetic. Conversely, it may be desirable for no incident light to be transmitted (opaque) through the coating to reveal only the coating's color. The deposition step can therefore form a coating with a thickness (vertical direction) of, for example, 0.5 µm, 1 µm, 1.5 µm, 2 µm, 2.5 µm, 3 µm, 3.5 µm, 4 µm, or 4.5 µm.Of course, depending on the application, the thickness could be greater, such as, for example, between 5 pm and 10 pm, without going out of the scope of the invention.

[0012] At least one partially closed contour of said at least one decoration of the timepiece may be formed solely by the step of depositing the coating using an electrohydrodynamic type droplet fluid by inkjet and the interior of each at least partially closed contour of said at least one decoration of the timepiece may be formed solely by a step of depositing another coating using an inkjet type droplet fluid (of the piezoelectric or thermal type).

[0013] This variant is preferred for large decorations, such as those with a horizontal dimension of at least 15 µm. Indeed, for the same surface area, electrohydrodynamic inkjet deposition is slower and more expensive to implement compared to piezoelectric or thermal inkjet deposition. Similar to cloisonné enamel, the closed contour(s) (one contour can enclose one or more other contours) are printed in high resolution, and then the interior (main surface) of each contour is printed in low resolution. This allows for a compromise between a finish equivalent to pad printing and a shorter overall printing time, while retaining the advantages mentioned above, such as customizing a piece on demand. (word, signature, drawings, etc.) at an advantageous cost. Of course, the outline can also be partially deposited by electrohydrodynamic inkjet deposition so that the missing part of the outline and the interior of the outline are produced by conventional inkjet deposition (piezoelectric or thermal type) in order to obtain lower production costs and times.

[0014] The deposition step may involve applying several adjacent drops to form a coating in a relatively flat layer on the timepiece. The drops will form a pattern in the form of a layer with a relatively constant thickness (vertical direction). Such a deposition can be used to create a decoration such as a Superluminova® hour ring, to create an electrical trace on the timepiece, or to selectively deposit an adhesive fluid to allow the timepiece to be bonded.

[0015] As a substitute for or in addition to the previous deposition, the deposition step may involve applying several overlapping drops to form a raised coating on the watch component. It is understood that the drops will form at least one pattern in the form of a stack of layers with a thickness (vertical direction) that varies depending on the fluid and the number of drops stacked in the same location.Such a stacking can provide a desired thickness, for example, in relation to an electrical conduction section to form an electrical fuse, to provide a curved thickness to improve the aesthetics (monochromatic or polychromatic) such as, for example, to offer nuances of colors, differences in saturation or even textures or artistic effects from the same fluid (at least one first drop being larger than at least one second drop and deposited in the same place) or to activate an epoxy glue by depositing the two constituents in the same location on top of each other to allow the bonding of the watch part or to deposit a first constituent on a first organ and a second constituent on a second organ, an activation such as a bonding of the first and second organs of the watch part being obtained by bringing the first and second constituents into contact.

[0016] The deposition step can apply drops, each with a dimension (diameter or height) less than or equal to 10 pm, which is defined as the dimension beyond which a human eye without a magnifying instrument can no longer distinguish two points. Advantageously, a drop dimension (diameter or height) between 1 pm and 2 pm has been obtained using an electrohydrodynamic inkjet device. The deposition step can therefore apply (deposit) drops, each with a dimension (diameter or height) equal to, for example, 1 pm, 2 pm, 3 pm, 4 pm, 5 pm, 6 pm, 7 pm, 8 pm, 9 pm, or 10 pm. Of course, depending on the application, such as that, for example, the bonding or metallization, the size of the drops could be greater such as, for example, between 10 pm and 25 pm, without going out of the scope of the invention.

[0017] The deposition stage can advantageously achieve a resolution of at least 2,500 dpi (dots per inch) according to the invention. This parameter is crucial for producing a high-quality decoration. Advantageously, a resolution of approximately 15,000 dpi has been achieved using an electrohydrodynamic inkjet device. Such a resolution overcomes current limitations and surpasses the human eye's ability to distinguish individual dots. The deposition step can therefore apply (deposit) drops at a resolution equal, for example, to 2500 dpi, 3000 dpi, 3500 dpi, 4000 dpi, 4500 dpi, 5000 dpi, 5500 dpi, 6000 dpi, 6500 dpi, 7000 dpi, 7500 dpi, 8000 dpi, 8500 dpi, 9000 dpi, 9500 dpi, 10000 dpi, 11000 dpi, 12000 dpi, 13000 dpi, 14000 dpi or 15000 dpi.Of course, depending on the application such as, for example, gluing or metallization, in which aesthetics are not a determining factor, the resolution could be less than 2,500 dpi without going out of the scope of the invention.

[0018] The deposition step can apply (deposit) drops each with a volume less than or equal to 1 pL (picoliters). More generally, the drops advantageously obtained according to the invention are on the order of femtoliters (fL) and no longer picoliters (pL), that is to say at least ten times less voluminous than with known ejection heads. The deposition step can therefore apply (deposit) drops with a volume equal to, for example, 0.1 fL, 0.2 fL, 0.3 fL, 0.4 fL, 0.5 fL, 0.6 fL, 0.7 fL, 0.8 fL, 0.9 fL, 1 fL, 2 fL, 3 fL, 4 fL, 5 fL, 6 fL, 7 fL, 8 fL, 9 fL, 10 fL, 20 fL, 30 fL, 40 fL, 50 fL, 60 fL, 70 fL, 80 fL, 90 fL, 100 fL, 150 fL, 200 fL, 250 fL, 300 fL, 350 fL, 400 fL, 450 fL, 500 fL, 550 fL, 600 fL, 650 fL, 700 fL, 750 fL, 800 fL, 850 fL, 900 fL, 950 fL or 1000 fL. Of course, depending on the application such as, for example, bonding or metallization, the volume of each drop could be greater than 1 pL without departing from the scope of the invention.

[0019] Advantageously, according to the invention, the deposition step can be used, for example, in addition to forming at least one decoration on the timepiece, to form at least one electrically conductive layer on the timepiece, to form at least one lubricating layer on the timepiece, or even to form at least one adhesive layer on the timepiece. Of course, other watchmaking applications are possible without departing from the scope of the invention.

[0020] By way of example, and not in any way limiting, a watch component can thus form all or part of a dial, a flange, an indicator, an appliqué, a hand, a case, a bracelet, a crystal, a control mechanism, a device escapement, resonator, power source, gear, spring, screw, bridge or plate.

[0021] The fluid is electrically conductive, that is to say, for example, it has an electrical conductivity of at least 0.1 pS. 1 .

[0022] The fluid may include colored pigments in order to give at least one predetermined color to the coating(s).

[0023] The coating can be opaque to the human visible spectrum, that is, no part of the incident light from the human visible spectrum is transmitted through the thickness of the coating to obtain only the tint(s) of the coating(s).

[0024] The portion of the blank onto which the coating is applied can be metal-based. Thus, the blank of the timepiece, and in particular the portion onto which the coating is applied, can include a metallic surface, for example, a blank coated with a metal-based layer or a blank that is itself metal-based. Advantageously, according to the invention, the process can therefore be applied to a new blank or a blank belonging to a timepiece already on the market in order to personalize it. It is understood that the process makes it possible to obtain a decorated timepiece with a rigid blank.

[0025] Finally, the invention also relates to the use of an electrohydrodynamic type inkjet device for depositing a decorative coating using a droplet fluid on a watch part with the advantages and results as explained above for the process of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features and advantages of the invention will become clear from the following description, which is given by way of example and not limitation, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of an example of a timepiece according to the invention; Figure 2 is a schematic view of an example of a timepiece according to the invention; Figure 3 is a schematic diagram of a nozzle of the electrohydrodynamic type according to the invention; Figure 4 is a schematic view of an example of an inkjet device of the electrohydrodynamic type according to the invention; Figure 5 is a schematic cross-sectional view of an example of a dial with a coating obtained by an inkjet deposition of the electrohydrodynamic type according to the invention; Figure 6 is a schematic cross-sectional view of a variant of the example in Figure 5. DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

[0027] In the various figures, identical or similar elements bear the same references, possibly with an additional subscript. Therefore, a description of their structure and function is not systematically repeated.

[0028] In all that follows, orientations are the orientations of the figures. In particular, the terms "upper", "lower", "left", "right", "above", "below", "forward" and "backward" are generally understood in relation to the direction in which the figures are represented.

[0029] Furthermore, the orientation terms are understood with respect to the orthogonal frame taken with reference to the normal orientation of an electrohydrodynamic nozzle 11, represented in Figure 4 and in which we distinguish: a longitudinal axis X, horizontal extending from the back to the front; a transverse axis Y, horizontal extending from the left to the right; and a vertical axis Z, extending from the bottom to the top.

[0030] The term "horizontal" is defined with respect to the XY plane, the terms "vertical plane" are defined with respect to a horizontal component projected along the vertical Z axis.

[0031] By "human visible spectrum" we mean the range of wavelengths between 380 and 780 nm as defined by the ISO / CIE 11664-3:2019 standard of the International Commission on Illumination "CIE".

[0032] By "opaque" we mean that no part of the incident light is transmitted, for example, through the thickness of the coating 1 B to give the watch part 1 only the tint(s) of the coating 1 B or of the coatings 1 B, 1C.

[0033] The term "droplet deposition of a fluid by inkjet" refers to the droplet ejection stage achieved by a conventional inkjet device, such as a piezoelectric or thermal type. For example, a voltage is selectively applied to a piezoelectric nozzle to utilize the contraction / expansion of the piezoelectric material to eject a predetermined quantity of fluid (droplet) contained within the nozzle. More specifically, the piezoelectric nozzle expands under the applied voltage, decreasing the volume of its cavity and forcing a quantity of fluid (droplet) to be expelled from the nozzle's outlet.

[0034] By "deposition of a fluid droplet by electrohydrodynamic inkjet," we mean the droplet ejection step achieved by an electrohydrodynamic inkjet device. An electrohydrodynamic nozzle 11 utilizes the conductivity of the fluids directly within the nozzle 11 (supplied by a conduit 14) and the interactions between electrostatic forces and the fluids. More specifically, the charges of the elements in a solution (possibly colloidal) are split into positive and negative ions with electrical characteristics due to the electrical potential difference between the nozzle 11 and a substrate (which can be the watch part 1 as in the example in Figure 3, an intermediate target 3 between the nozzle 11 and the watch part 1 as in the example in Figure 4, or a target (not visible) positioned so that the watch part 1 is between the nozzle 11 and the target).

[0035] After a potential is applied by a voltage generator 13, the difference in this potential between the nozzle 11 and the substrate 1, 3 will cause the electrical repulsive forces to create a substantially spherical curved surface (meniscus 12 in Figures 3 and 4) of the fluid at the nozzle outlet 11. The charges in the fluid will separate into positive and negative ions due to the strong electrical force in the meniscus 12, so that tiny droplets 12A form in the part furthest from the meniscus 12 (lower dome) relative to the nozzle 11. The resistance and energy required for extraction (ejection) are therefore low and allow better control of the generation of droplets 12A.

[0036] Several types of electrohydrodynamic ejection modes exist, depending on the different fluid properties and the applied potential (voltage) parameters. For example, in a microdroplet mode, the electric field strength at the tip of the nozzle 11 is sufficiently strong to cause the meniscus 12 to form a hemisphere or ellipse. Then, droplets 12A, much smaller than the outer diameter of the nozzle 11, form at the lowest point of the meniscus 12, where the electric field is concentrated. Consequently, the maximum size—specifically, the largest diameter or height—of the droplets 12A can be limited to a few micrometers, thus offering very high deposition accuracy and resolution.Other ejection modes from an electrohydrodynamic nozzle 11 are also possible, such as pulsed conical ejection (droplet from a conical meniscus) or continuous ejection (droplets linked together).

[0037] The term "based on" refers to a material or alloy comprising at least 50% by total mass or weight of a given element, such as 51%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100% by total mass. Of course, in the case of a material or alloy containing at least three elements, the expression "based on a first element" means a material or alloy consisting primarily of... in total mass or weight of said first element, which may in this case be less than 50% of the total mass. In what follows, unless otherwise indicated, all percentages (%) shown are percentages by total mass or weight.

[0038] By "polymer" we mean all materials formed from at least one polymer chain, sometimes called a fiber, of varying lengths, which can be of natural or synthetic origin.

[0039] By "ceramic" we mean all materials in crystalline and / or amorphous form based on an oxide, carbide, sulfide or nitride, especially metallic such as aluminium oxide (alumina, Al2O3), silicon oxide (SiC>2), silicon nitride (SiN) or silicon carbide (SiC).

[0040] By "horological component 2", we mean all types of timekeeping or measuring instruments such as clocks, small clocks, watches, etc...

[0041] By "watch movement 4", we mean all types of mechanisms capable of counting time whether they are powered by mechanical energy (e.g. a barrel) or electrical energy (e.g. a battery).

[0042] By "housing 6" we mean all types of devices capable of containing, displaying, decorating and / or controlling a watch movement 4 such as, for example, all or part of a case, a bracelet or a display.

[0043] The watch part 1 was developed to be integrated into a watch part 2 as illustrated for example in figure 1. Thus, the watch part 1 can form all or part of a watch case 6 such as all or part of a dial or rehaut, a display such as an indicator 5, an applique 7A, a hand 7B or a disc, a case, a bracelet, a crystal or a control organ such as a crown or a push-button. The watch part 1 can also form all or part of a watch movement 4 such as all or part of an escapement device such as a Swiss lever mechanism, a resonator such as a balance-spring mechanism or a quartz tuning fork 1A as illustrated in figure 2, a power source such as a barrel, an automatic winding system or a battery, a gear train such as a mobile or a toothed wheel, a spring, a screw, a bridge or a plate.

[0044] To achieve the purpose of the invention, the process includes a first step intended to provide a blank T of the watch part 1 to be decorated, then a second step intended to deposit a coating 1 B on at least a part of the blank 1' to form the decorated watch part 1 which offers a precision and a result equivalent or even superior to pad printing while limiting the necessary investment without any real aesthetic limit.

[0045] Preferably, the blank 1' and in particular the part of the blank T on which the coating 1 B is deposited may include a metallic surface, for example a A blank at least partially coated with a metal-based layer, or a blank that is metal-based. For example, the blank T may be brass or steel-based and include at least a partial surface to be decorated. Alternatively, the blank T may include a core made of polymer material, at least a part of whose surface is metallized. The blank T is thus generally rigid, providing a firm support for the decorative coating 1B, 1C. Advantageously, according to the invention, the method can therefore be applied to a new blank T or to a blank T belonging to a watch component 2 already on the market in order to personalize it. This rigidity can be obtained, for example, from a thickness (vertical direction Z) of the blank T of at least 0.2 mm and preferably at least 0.4 mm.

[0046] Of course, an intermediate layer (between the metal and coating 1B, 1C) can be used to improve the adhesion (better bonding between the metal and coating 1B, 1C) and / or the aesthetics (better contrast between the metal and coating 1B, 1C) of the decoration. Such an intermediate layer can be, for example, made of a transparent, semi-transparent, or opaque polymer.

[0047] The invention generally relates to the use of an electrohydrodynamic inkjet device 10 for depositing a coating 1 B using a droplet fluid 12A on a watch part 1. Typically, the invention relates in particular to a method for manufacturing a watch part 1 comprising a step of depositing a coating 1 B on at least a part of the blank T using a droplet fluid by electrohydrodynamic inkjet intended to form at least one decoration of the watch part 1.

[0048] Advantageously, the process according to the invention uses an electrohydrodynamic (EHD) inkjet deposition system, which allows for versatile deposition on demand (continuous, semi-continuous, spot, etc.). In other words, the type of droplets (shapes, frequency, dimensions, etc.) can be easily adapted to the requirements. The device is simply controlled by the voltage generator, which induces pulses with a relatively high voltage amplitude, such as, for example, between 1 kV and 5 kV, i.e., for example, 1 kV, 1.5 kV, 2 kV, 2.5 kV, 3 kV, 3.5 kV, 4 kV, 4.5 kV, or 5 kV.

[0049] Thus, the electrohydrodynamic nozzle 11 uses a simple potential difference to eject a droplet 12A much smaller than the meniscus 12 of fluid at the nozzle outlet, as illustrated in Figure 4. By selectively controlling the potential difference, it is therefore very simple to parameterize the frequency and timing at which the droplets 12A are ejected, with a dimension (diameter or height) approximately ten times smaller than with known ejection heads such as the piezo- type. electric. This results in a deposit that becomes compatible with watchmaking in general, with resolutions and rendering at least equivalent to those of pad printing, without the limitations in terms of production costs and fluids.

[0050] In the example illustrated in Figure 4, the electrohydrodynamic inkjet device 10 includes an intermediate target 3 between the nozzle 11 and the watch part 1. This device 10 is preferred because it allows the watch part 1 to be completely independent of the device 10. The device 10 can thus be moved above the watch part 1, or conversely, the watch part 1 can be moved below the device 10, or both the watch part 1 and the device 10 can be movable relative to each other to obtain the desired deposition pattern for each watch part 1, which notably allows for lower-cost mass production while enabling a very wide variety of different possible depositions between each watch part 1.

[0051] Each droplet 12A ejected from the nozzle 11 passes through the intermediate target 3 by at least one through hole 3A in order to be deposited on the watch part 1. In such a configuration, the vertical working distance (Z-axis) between the watch part 1 and the intermediate target 3 can be, for example, between 0.2 mm and 2 mm, i.e. for example equal to 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm or 2.0 mm. Of course, depending on the application, the distance could be less or greater without going outside the scope of the invention.

[0052] The type of fluid is highly varied (metallic, aqueous, polymeric, ceramic). Generally, the fluid used may contain colored pigments (or even a coloring chemical in a variety of materials) in a conductive medium or binder. The binder may be aqueous. In one variation, a UV-sensitive fluid may be formulated to harden when exposed to ultraviolet (UV) light in order to fix the deposit made on the watch component 1. Another variation may involve using a fluid sensitive to a gas such as air (oxidation) to fix the deposit made on the watch component 1. Preferably, UV-sensitive fluids are used because they dry very quickly, resulting in sharper and more vibrant designs. Solvent-based fluids that dry rapidly through the evaporation of one or more solvents may also be used.

[0053] Advantageously, the electrohydrodynamic inkjet deposition according to the invention can use fluids of virtually any viscosity. Typically, viscosities ranging from 0.5 to 10,000 cP (1 centiPoise = T 10⁻¹⁰). 3 Pa s) have been successfully tested. However, the fluids used must necessarily be electrically conductive, even with very low polarity, for the process according to the invention, the fluid may have an electrical conductivity of at least 0.1 pS nr. By way of example, and not in any way limiting, the fluid may have an electrical conductivity of at least 0.1 pS nr. 1 .

[0054] Typically, the same type of watch part 1 or not, using the same tooling (same device 10), can mass-produce a number of different deposits on each watch part 1 without any real limit. Thus, for example, depending on the type of fluid present on each ejection nozzle 11, a first part 1 can receive a first deposit pattern with a first type of fluid, a second part 1 can receive a second deposit pattern with the first type of fluid, a third part 1 can receive the first deposit pattern with a second type of fluid, a fourth part 1 can receive the first deposit pattern with the first type of fluid and the second deposit pattern with the second type of fluid, and so on, without each part 1 being significantly more expensive to produce than another.

[0055] The process according to the invention offers an unprecedented technological change by pushing back traditional limits and redrawing the field of possibilities with its viscosity tolerance of droplets 12A up to 10,000 cP, droplet sizes 12A less than 1 pm (micrometer) and printheads with several hundred (or even thousands) of nozzles 11 containing one fluid (or several different fluids).

[0056] Finally, any type of watch component 1 (flat or raised) may advantageously include, primarily or partially on its external surface, the coating thus formed by a droplet deposition according to the invention. It is understood in particular that a wide variety of fluids deposited as droplets – the material of the watch component – ​​can be considered to form the decorative coating without being limited to printing solely by electrohydrodynamic inkjet printing, that is to say, in particular combined with another type of printing, while maintaining a result at least equivalent to pad printing, with the advantage of being able, for example, to personalize a component on demand (word, signature, designs, etc.).), but also combined applications that are both technical and aesthetic, such as lubrication, bonding, metallization or more generally a selective deposition of a very precise coating which is not necessarily intended to be visible on the final application of the watch part 1 such as, for example, to form an authentication pattern which is not visible to the naked eye without magnification and / or without special illumination.

[0057] Advantageously, according to the invention, the deposition step can be intended, for example, in addition to forming at least one decoration on the timepiece 1 such as an indicator 5 (number of a date disc) of the timepiece 2 of Figure 1, to forming at least one electrically conductive layer 9 on the timepiece 1 such as a quartz tuning fork 1A in Figure 2, to forming at least one lubricating layer on the timepiece 1 such as a ruby ​​bearing of the watch movement 4 of Figure 1 or even to form at least one luminescent adhesive layer on the watch component 1, such as an applique 7A of Figure 1, for gluing it to the dial 8 while also being luminescent. Of course, other watchmaking applications are possible without departing from the scope of the invention.

[0058] Said at least one decoration of the watch part 1 is preferentially formed solely, that is to say exclusively, by the step of depositing the coating 1 B using a droplet fluid 12A by electrohydrodynamic inkjet as, for example, illustrated in figure 5 for a dial 8. An optimal resolution of the whole of each decoration formed is then obtained and it is possible to obtain a decoration with a wide variety of colors with a rendering of better quality than pad printing or conventional inkjet printing (of the piezoelectric or thermal type).

[0059] According to a variant illustrated in Figure 6 for an example of application to a dial 8, said at least one decoration of the timepiece 1 is formed by at least one closed contour whose interior is filled. Thus, preferably, said at least one closed contour of said at least one decoration of the timepiece 1 is formed solely by the step of depositing the coating 1B using an electrohydrodynamic type inkjet droplet fluid, and the interior of each closed contour of said at least one decoration of the timepiece 1 can be formed solely by a step of depositing another coating 1C using an inkjet droplet fluid such as, for example, a piezoelectric or thermal type.

[0060] This variant is preferred for large decorations, such as those with a horizontal dimension (X and / or Y axis) of at least 15 µm. Indeed, for the same surface area, electrohydrodynamic inkjet deposition is slower and more expensive to implement compared to piezoelectric or thermal inkjet deposition. Similar to cloisonné enamel, the closed contour(s) (one contour can enclose one or more other contours) are printed in high resolution, and then the interior (main surface) of each contour is printed in low resolution. This allows for a compromise between a finish equivalent to pad printing and a shorter overall printing time, while retaining the advantages mentioned above, such as customizing a watch component on demand (word, signature, designs, etc.) at a competitive cost.

[0061] The deposition step can form a coating 1B with a thickness E (vertical direction Z) of less than 5 µm. Advantageously, according to the invention, the coating 1B can be deposited very thinly, which makes it possible, in particular, to faithfully reproduce the reliefs of the upper surface of the blank 1'. Indeed, depending on the desired aesthetic effect, it may be desirable for a portion of the incident light to be transmitted (partial transparency) through the thickness E of the coating 1B, 1C to partially reproduce the color of the area beneath the coating 1B, 1C (such as the blank 1' of the timepiece 1) to create a specific aesthetic. Conversely, it may be desirable for no part of the incident light to be transmitted (opaque coating 1B) through the thickness of the coating 1B to reveal only the color(s) of the coating 1B or the coatings 1B, 1C. The deposition step can therefore form a coating 1B, 1C with a thickness E (vertical direction) equal, for example, to 0.5 pm, 1 pm, 1.5 pm, 2 pm, 2.5 pm, 3 pm, 3.5 pm, 4 pm, or 4.5 pm. Of course, depending on the application, the thickness E could be greater, such as, for example, between 5 pm and 10 pm, without departing from the scope of the invention.

[0062] Thus, depending on the thickness E and the composition of the ink, the decorative coating 1B, 1C can be substantially opaque, that is to say, it allows transmission across the entire visible human spectrum through the coating 1B, 1C of at most 10%, such as, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%. 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10% and preferably no more than 5% such as, for example, 0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, 2.25% 2.5%, 2.75%, 3%, 3.25%, 3.5%, 3.75%, 4%, 4.25%, 4.5%, 4.75%, or 5%.

[0063] The deposition step can be designed to apply several adjacent drops 12A to form the coating 1B in a substantially flat layer on the timepiece 1. It is understood that the drops 12A will form a substantially horizontal pattern (XY plane) in the form of a layer of substantially constant thickness E (vertical Z direction). Such a deposition can be used to create a decoration such as an hour ring in Superluminova®, to fill a recess for an appliqué 7A or a hand 7B with Superluminova®, to form an electrical trace 9 on the timepiece 1, or to selectively deposit an adhesive fluid to allow the bonding of the timepiece 1.

[0064] As a substitute for or in addition to the previous deposition, the deposition step can be designed to apply several superimposed drops 12A to form the coating 1B in a raised layer (thickness along the Z-axis not constant) on the timepiece 1. It is understood that the drops 12A will form at least one substantially horizontal pattern (XY plane) in the form of a stack of layers with a thickness (vertical Z-direction) that varies depending on the fluid and the number of drops 12A stacked at the same location. Such a stacking can provide a desired thickness, for example, relative to an electrical conduction section to form an electrical fuse, or provide a convex thickness to improve aesthetics (monochromatic or polychromatic), such as, for example, to offer a color gradient from the same fluid (at least one drop being larger than the others). minus a second drop and deposited in the same place), to activate an epoxy glue by depositing the two components of the epoxy glue one on top of the other in the same location to allow the bonding of the watch part 1 or to deposit a first component on a first organ and a second component on a second organ, an activation such as a bonding of the first and second organs of the watch part 1 being obtained by bringing the first and second components into contact.

[0065] The deposition step can apply 12A drops, each with a dimension (diameter or height) less than or equal to 10 pm, which is defined as the dimension beyond which a human eye, without a magnifying instrument, is no longer able to distinguish two points. Advantageously, a dimension (diameter or height) of 12A drops between 1 pm and 2 pm has been obtained using an electrohydrodynamic inkjet device. The deposition step can therefore apply (deposit) 12A drops, each with a dimension (diameter or height) equal to, for example, 1 pm, 2 pm, 3 pm, 4 pm, 5 pm, 6 pm, 7 pm, 8 pm, 9 pm, or 10 pm. Of course, depending on the application such as, for example, bonding or metallization, the size of the 12A drops could be larger such as, for example, between 10 pm and 25 pm, without going out of the scope of the invention.

[0066] By depositing coating 1B using a droplet fluid 12A via electrohydrodynamic inkjet in a single pass over the surface to be decorated, the thickness E (vertical Z direction) of coating 1B is typically several hundred nanometers (e.g., between 400 and 600 nm), because the droplets 12A spread across the surface after deposition. Naturally, the thickness E (vertical Z direction) of coating 1B increases with each subsequent deposition pass. Therefore, the deposition step of coating 1B may involve two or more passes in order, for example, to obtain a thickness E (vertical Z direction) of coating 1B greater than 1 pm.

[0067] The deposition stage can advantageously achieve a resolution of at least 2,500 dpi (dots per inch) according to the invention. This parameter is crucial for producing a high-quality decoration. Advantageously, a resolution of approximately 15,000 dpi has been achieved using an electrohydrodynamic inkjet device. Such a resolution overcomes current limitations and surpasses the human eye's ability to distinguish individual dots. The deposition step can therefore apply (deposit) 12A drops at a resolution equal to, for example, 2500 dpi, 3000 dpi, 3500 dpi, 4000 dpi, 4500 dpi, 5000 dpi, 5500 dpi, 6000 dpi, 6500 dpi, 7000 dpi, 7500 dpi, 8000 dpi, 8500 dpi, 9000 dpi, 9500 dpi, 10000 dpi, 11000 dpi, 12000 dpi, 13000 dpi, 14000 dpi, or 15000 dpi. Of course, depending on the application, such as, for example, bonding or metallization, in which Aesthetics are not a determining factor; the resolution could be less than 2500 dpi without departing from the scope of the invention.

[0068] The deposition step can apply (deposit) 12A droplets, each with a volume less than or equal to 1 pL (picoliters). More generally, the droplets advantageously obtained according to the invention are on the order of femtoliters (fL) and no longer picoliters (pL), that is to say, at least ten times less voluminous than with known ejection heads. The deposition step can therefore apply (deposit) 12A drops with a volume equal, for example, to 0.1 fL, 0.2 fL, 0.3 fL, 0.4 fL, 0.5 fL, 0.6 fL, 0.7 fL, 0.8 fL, 0.9 fL, 1 fL, 2 fL, 3 fL, 4 fL, 5 fL, 6 fL, 7 fL, 8 fL, 9 fL, 10 fL, 20 fL, 30 fL, 40 fL, 50 fL, 60 fL, 70 fL, 80 fL, 90 fL, 100 fL, 150 fL, 200 fL, 250 fL, 300 fL, 350 fL, 400 fL, 450 fL, 500 fL, 550 fL, 600 fL, 650 fL, 700 fL, 750 fL, 800 fL, 850 fL, 900 fL, 950 fL or 1000 fL. Of course, depending on the application such as, for example, bonding or metallization, the volume of each drop 12A could be greater than 1 pL without departing from the scope of the invention.

[0069] The initial results, highlighted by routine parameterization tests of device 10 according to the fluid to be deposited, should allow for finer droplet sizes of around 0.2 pm.

[0070] By way of example, and by no means limiting the application of the invention, one can imagine obtaining, using the process according to the invention, raised or flat decorations, printing on flat or curved surfaces, selective metallization, lubricant distribution, adhesive applications, on-demand customization, authentication, etc., without changing the device 10. It is thus possible, in particular, to create diffractive decorations by directly printing submicron structures onto a watch component 1' blank 1', such as a watch dial 8. One can also imagine creating OLED-type prints using special fluids (for example, quantum dots) on a watch component 1. It is also conceivable to directly print submicrometer (or a few micrometers) electrical traces invisible to the naked eye, enabling the inductive charging of a battery, the creation of RFID devices, or solar power.Finally, the process according to the invention also allows the direct printing of semiconductors and / or focusing microlenses for a solar device comprising, for example, at least one photovoltaic cell.

[0071] The invention is not limited to the embodiments and variations shown, and other embodiments and variations will be obvious to those skilled in the art. Thus, the above embodiments are examples. Simple features of different embodiments can also be combined and / or interchanged to provide other embodiments.

[0072] Furthermore, the invention is not limited to the watchmaking field. Thus, the invention could also be applied in other fields such as, for example, jewelry, leather goods, tableware, optical instruments, firearms or writing instruments. LIST OF REFERENCES 1 - watch part T - draft 1A - resonator 1 B - coating 1C -other coating 2 - timepiece 3 - intermediate target 3A - through hole 4 - clockwork movement 5 - indicator 6 - dressing 7A - wall light 7B -needle 8 - dial 9 - electrically conductive track 10 - Electrohydrodynamic type inkjet device 11 - nozzle 12 - Meniscus 12A - drop 13 - Pulse voltage generator 14 - Fluid supply line E - thickness of the deposit

Claims

DEMANDS 1. A method for manufacturing a watch component (1) forming all or part of a watch case (6) or a watch movement (4), characterized in that it comprises the following steps: - to obtain a rough draft (T) of the watch part (1) to be decorated; - deposit a coating (1 B) on at least part of the blank (T) using a droplet fluid (12A) by electrohydrodynamic inkjet intended to form at least one decoration of the watch part (1).

2. Method according to the preceding claim, wherein said at least one decoration of the watch part (1) is formed solely by the step of depositing the coating (1B) using a droplet fluid (12A) by electrohydrodynamic inkjet.

3. Method according to the preceding claim, wherein the deposition step forms a coating (1 B) of a thickness (E) less than 5 pm.

4. Method according to claim 1, wherein at least one at least partially closed contour of said at least one decoration of the watch part (1) is formed solely by the step of depositing the coating (1B) using a droplet fluid (12A) by electrohydrodynamic inkjet and the interior of each at least partially closed contour of said at least one decoration of the watch part (1) is formed solely by a step of depositing another coating (1C) using a droplet fluid by inkjet.

5. A method according to any one of the preceding claims, wherein the deposition step is intended to apply several adjacent drops (12A) to form the coating (1B, 1C) in a substantially flat layer on a blank (T) of the watch part (1).

6. A method according to any one of the preceding claims, wherein the deposition step is intended to apply several superimposed drops (12A) to form the coating (1B, 1C) in relief layer on a blank (T) of the watch part (1).

7. A method according to any one of the preceding claims, wherein the deposition step applies drops (12A) each of a dimension less than 10 pm.

8. A method according to any one of the preceding claims, wherein the deposition step has a resolution of at least 2,500 dpi.

9. A method according to any one of the preceding claims, wherein the deposition step applies drops (12A) each of a volume less than or equal to 1 pL.

10. A method according to any one of the preceding claims, wherein the watch component forms all or part of a dial (8), a flange, an indicator (5), an applique (7A), a hand (7B), a case, a bracelet, a crystal, or a control element.

11. A method according to any one of claims 1 to 9, wherein the watch component forms all or part of an escapement device, a resonator (1A), a power source, a gear train, a spring, a screw, a bridge, or a mainplate.

12. A method according to any one of the preceding claims, wherein the fluid is electrically conductive and comprises colored pigments.

13. A method according to any one of the preceding claims, wherein the coating (1B, 1C) is opaque over the human visible spectrum.

14. A method according to any one of the preceding claims, wherein the part of the blank (1') on which the coating (1B, 1C) is deposited is metal-based.

15. Use of an electrohydrodynamic type inkjet device (10) for depositing a decorative coating (1 B) using a droplet fluid (12 A) on a watch part (1).

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