EP3067150A1 - Method for decorating a timepiece and timepiece obtained by such a method - Google Patents

Abstract

Method for decorating a dial, characterized in that it comprises a step of etching (E1) a pattern on a tampon printing plate by a femtosecond laser, and then comprising a decal step (E20) of said pattern on the dial using the pad printing plate.

Description

The invention relates to a method for decorating a timepiece, in particular a watch element. It also relates to a watch element as such obtained by the implementation of such a method. Finally, the invention also relates to a timepiece, in particular a watch, for example a wristwatch, comprising such a watchmaking element

When it is desired to make a decoration on a timepiece, such as a dial, it is known to carry out a surface treatment, traditionally by a grinding or decaling method, for example. Such an approach of the state of the art comprises a single step of machining the surface to be decorated, to achieve a chosen surface effect. As a variant, markings may be made, for example by a decal, which makes it possible to record inscriptions on the surface, generally using a stamp comprising an engraved and inked plate.

The existing decorating solutions are unsatisfactory. Indeed, it should be noted that horological applications are very demanding for such a decoration process: the aesthetic appearance obtained is very important and the grinding, coloring and / or marking must be free of defects or burrs. Finally, the possibilities of decoration offered by these existing solutions are limited to a limited choice among some old and well known solutions, which does not allow to offer original decorative solutions.

The object of the invention is to provide a method of decorating a timepiece, in particular a dial, which makes it possible to achieve in a simple manner a precise and attractive aesthetic appearance, and durable over time.

For this purpose, the decoration method comprises a step of etching a pattern on a tampon printing plate by a femtosecond laser, and then comprises a step of decalting said pattern on a dial using the pad printing plate. This decoration process is advantageously combined with a step of structuring the surface of the surface to decorate the dial.

A decorative method and a dial and a timepiece according to the invention are defined by the claims.

• La figure 1 représente schématiquement les étapes du procédé de décoration selon un mode de réalisation de l'invention.
• La figure 2 représente schématiquement un plan d'une décalque selon un mode de réalisation de l'invention.
• La figure 3 représente schématiquement en vue de dessus un élément horloger obtenu après décoration selon le mode de réalisation de l'invention.
• La figure 4 représente les mesures de couleur obtenues sur des échantillons lors de la mise en oeuvre de tout et partie des étapes du procédé de décoration selon trois exemples de mise en oeuvre d'un mode de réalisation de l'invention.

These objects, features and advantages of the present invention will be set forth in detail in the following description of a particular embodiment made in a non-limiting manner in relation to the appended figures among which:

• The figure 1 schematically represents the steps of the decoration method according to one embodiment of the invention.
• The figure 2 schematically represents a plane of a decal according to one embodiment of the invention.
• The figure 3 schematically shows a top view of a watch element obtained after decoration according to the embodiment of the invention.
• The figure 4 represents the color measurements obtained on samples during the implementation of all and part of the steps of the decoration process according to three exemplary embodiments of one embodiment of the invention.

According to the embodiment of the decoration method of the invention, the possibilities offered by femtosecond laser machining are used to produce a tampon printing plate, which will be used in a step for decorating a timepiece, made of solid material. metallic or non-metallic, in particular in combination with another decoration technique according to one embodiment. This approach has the advantage of greatly increasing the decorative possibilities of a watch element.

The invention will now be illustrated in a nonlimiting manner in the context of the decoration of a watch face. It could naturally be used to decorate another watch element, a wristwatch or a watch movement, such as for example and without limitation, a bezel, blanks or movement supplies.

The decoration method according to the embodiment first comprises an etching step E1 of a tampon printing plate using a femtosecond laser, to form a decoration pattern. The femtosecond laser is used in such a way that it makes it possible to generate an engraving whose extreme fineness obtained then makes it possible to trace very fine patterns on the dial, in particular patterns formed by fine lines corresponding to the engravings of the photograph. According to the embodiment, this very fine pattern makes it possible to obtain surprising and seductive effects, such as, for example, a color rendering that is different from the color of the base ink of the plate and the color of the bottom of the dial, as this will be specified later. The use of a femtosecond laser machining technique to produce a pattern intended to be printed by pad printing thus opens up very interesting new possibilities for producing watch dials, and more generally any watchmaking element.

A femtosecond laser is a particular type of laser that produces ultra-short pulses whose duration is of the order of a few femtoseconds to a few hundred femtoseconds (1 fs = 1 femtosecond = 10 ^-15 seconds). Thus, for etching a metal plate, the femtosecond laser can for example generate pulses with a wavelength of 1030 nm, energy of 20 μJ, with a pulse rate of 500 kHz and a pulse duration of 270. fs. Of course, these numerical values are given by way of example and can take other values. The wavelength can be variable within a range ranging from 300 nm to 1100 nm, typically 343 nm for glass or alumina. The duration of the pulses can be variable in a range from 200 fs to 500 fs.

An optical system is used to shape the beam, composed of different elements in order to adjust the energy delivered, the polarization and the size of the beam. The beam is scanned on the target (surface of the tampon printing plate) by an electronically controlled optical beam deflection device. It allows to achieve the desired patterns via a control software. For example, F-Theta lenses are used in the embodiment, 100 mm and 160 mm focal length, respectively, to allow machining on a respective surface (field) of diameter 72 mm and 121 mm. The use of a F-Theta lens of 60 mm focal length reduces the surface (field) to a diameter of 46 mm. The scanning head is driven by a marking software associated with a digital control card for synchronizing the movement of the beam with the laser shot. This set allows among other things to change the speed of displacement of the laser beam on the surface to be engraved, the laser scanning strategy and finally the number of passages on the same area. The micro-positioning system is driven along five axes, three translation axes and two axes of rotation. The depth of the etching obtained can be adjusted with the number of passes, and thus the number of repetitions of the scanning pattern: the higher the number of passes, the deeper the recess will be. In all cases, the removal of material resulting from this etching step causes the realization of a hollow of an average depth greater than or equal to 4 microns.

Thus, the decoration method comprises a particular E20 decal step, distinct or including any other traditional markings mentioned below, from the pad printing plate developed in the previous step E1 described above. The superposition of such a decal on the surface of the dial to decorate achieves unexpected effects.

The invention does not relate to the design produced by this etching step, which allows to form all curves by moving the beam along a selected path, in particular lines, parallel or substantially parallel.

The decorating process may include optional additional steps. This complete process, including the optional steps, is illustrated by the figure 1 .

According to one embodiment, the decoration method comprises a preliminary step of preparing the surface of the dial to be treated. For this, the plate that forms the dial, which is for example made of metallic material such as brass, is polished, washed and degreased. Alternatively, the dial, or any other watch element to be decorated, may be in another metallic material, the term metal including a pure metal or any metal alloy, such as steel, titanium, gold or platinum. Alternatively, one could also imagine a watch element comprising a ceramic base plate, for example made of zirconia or alumina, silicon, glass, sapphire, mother-of-pearl or mineral material, whose bottom shows the natural color of the material or is colored in a given color, for example in white.

Optionally, the decoration method comprises a complementary E2 treatment step of satin, brushing, or spraying. This step E2 can be performed at any time of the decoration process before the decal step E20.

Similarly, optionally, the decoration method comprises a step of depositing an optional layer E3, preferably having a thickness of between 0.2 and 1 μm, to protect the dial against oxidation and / or color.

Next, the method according to the embodiment optionally comprises a step of depositing E4 with a metal layer. Preferably, this deposited metal comprises silver, which is sufficiently malleable to be structured during the following operations, in particular a surface structuring step E10. It is of course possible to deposit a layer of a malleable metal other than silver to facilitate the realization of machining.

This surface structuring step E10 comprises a decoration machining of the surface to be decorated of the watch element, which may be, according to an advantageous example, a sunburst, which consists of superficially scratching the surface of the dial with a brush and / or a paste abrasive. In a variant, this step may involve spraying and / or sanding. In the case of a sunburst, a fine line array will be made, for example in a layer of silver, as will be mentioned later and which gives the room the appearance of a sun.

• Le satinage, le brossage, qui donnent comme le giclage une texture très fine et peu profonde ;
• L'azurage, consistant en la réalisation de fins cercles concentriques qui animent une surface ;
• Le diamantage, un polissage très soigné ;
• La réalisation de Côtes de Genève, qui forment un motif de zones brossées en bandes, de largeur et finesse variables, et d'angle et d'écart plus ou moins prononcé entre les bandes de côtes. L'abrasif ou la brosse marque la surface de stries parallèles, droites ou circulaires, qui forment les côtes ;
• Le perlage, qui est un décor formé de cercles à traits concentriques très rapprochés, voire empiétant les uns sur les autres ;
• Le colimaçonnage, qui est un décor en forme de spirale, obtenu au moyen d'une meule que l'on fait tourner sur la surface de la pièce en l'orientant de manière à obtenir des traits en forme de spirale.

One can of course imagine using a technique other than sunburst, spray, sanding, mentioned above, in this surface structuring step, depending on the final appearance that is desired to give the dial. By way of example, here are other possible techniques that can be implemented in this surface treatment:

• The satin, the brushing, which give as the spray a very fine and shallow texture;
• The whitening, consisting of the realization of fine concentric circles which animate a surface;
• Diamonding, a very polished polishing;
• The realization of Côtes de Genève, which form a pattern of brushed zones in bands, of variable width and fineness, and of angle and more or less pronounced difference between the rib bands. The abrasive or brush marks the surface of parallel striations, straight or circular, which form the ribs;
• Beadwork, which is a decoration formed of circles with concentric features very close to each other, or even encroaching on each other;
• The snaking is a spiral-shaped decoration obtained by means of a grinding wheel which is rotated on the surface of the piece, orienting it so as to obtain spiral-shaped lines.

Finally, the surface structuring achieves a shallow decoration by striking the surface of the piece in a controlled manner. The tools used may be, for example, abrasive-coated pads or brushes. This surface structuring step forms a surface roughness of preferably between 0.05 and 0.1 μm. So, we call surface structuring any stage which makes it possible to generate a modification of the surface to be decorated on a thin thickness, less than or equal to 1 μm, or even 0.3 μm, or even 0.1 μm. This patterning forms stripes on this specified thickness, preferably sufficiently dense to be visible, and regular and organized, forming a particular pattern providing an attractive visual appearance.

A layer or series of coloring layers may then be optionally deposited in a step E5 preceding the decal step E20, for example via one or more galvanic layer (s), and or one or more layers formed by PVD deposition (physical vapor deposition), and / or one or more layers (s) formed by deposition ALD (atomic layer deposition, according to the acronym "Atomic Layer Deposition"), or by any other deposition technique for forming a coating that may change the perceived color of the dial. It is conceivable to deposit the colored layer on part of the dial only by masking techniques, or to deposit several different colored layers at different locations on the surface of the dial.

The decoration method has been illustrated previously by way of example, and it is conceivable to reverse the order of certain steps, such as to carry out the surface structuring, especially the sunburst, after a step of depositing a layer of color, for example.

In general, a varnish is then deposited, then a traditional decal can be applied with markings (letters, numbers, indexes, railway, other signs) on the dial.

Finally, the decoration process comprises the particular E20 decal step mentioned above, distinct or including any other traditional markings mentioned above, from the pad printing plate developed in the previous step E1 described above. The superposition of such decal on the previously elaborated surface allows to reach unexpected effects.

It is conceivable to reverse the order of the last steps, such as making the E20 decal before the traditional decal and / or the deposition of the varnish.

Optionally, the completed dial may also include sconces, such as indexes with luminescent material or kittens set with precious stones.

• Diamètre faisceau laser à la focale : 20 à 40 µm ;
• Ecart latéral entre 2 gravures : entre 100 et 250 µm ;
• Profondeur de gravure : 15 µm.

The Figures 2 and 3 illustrate an example of implementation of the decoration method described above. The figure 2 first shows the decal plane. This result was obtained using a femtosecond laser, and with the following parameters to form the engravings on the tampon printing plate:

• Laser beam diameter at the focal length: 20 to 40 μm;
• Lateral gap between 2 engravings: between 100 and 250 μm;
• Depth of engraving: 15 μm.

The lateral and longitudinal recovery rates are between 0% and 99%; they are 0% and 95% respectively for this embodiment. The power densities must be greater than the ablation threshold of the material, and are typically of the order of 4.19 × 10 ⁶ MW / cm ² .

The figure 3 shows the final decoration obtained on the dial after the stamping step E20 by pad printing, applied on a surface structure consisting of a sunburst.

• A titre d'exemple, lorsque le motif du cliché de tampographie présente des lignes de 150 µm de large et espacées de 150 µm, alors le résultat obtenu est intéressant. Dans un tel cas, les différentes lignes individuelles sont distinguées par l'oeil. Un tel cas peut être atteint pour des lignes d'épaisseur comprises entre 100 et 300 µm inclus et/ou espacées de 100 à 300 µm inclus ;
• Lorsque les deux dimensions précédentes (largeur de lignes et espace entre les lignes), qui peuvent être égales ou différentes, et régulières ou irrégulières, mais formant de préférence une trame régulière, sur un même motif, sont encore réduites, par exemple inférieures ou égales à 100 µm, voire inférieures ou égales à 70 µm, voire inférieures ou égales à 60 µm, alors l'oeil ne parvient plus à distinguer les différentes lignes individuelles et les combine, ce qui permet de créer des effets inédits, par exemple à l'aide d'illusions d'optique. L'exemple de la figure 2 est proche de cette configuration puisqu'il comprend des lignes 10 de 100 µm de large, espacées de 250 µm.

The fact of using thin lines parallel and close together during the pad printing step makes it possible to achieve particularly advantageous results. The engraving depth of the plate (also indirectly the width of the engraving and the thickness of the lines formed) and the lateral distance between two engravings of the tamponade are two important criteria for forming aesthetic effects:

• By way of example, when the pattern of the tampon printing plate has lines 150 μm wide and spaced 150 μm apart, the result obtained is interesting. In such a case, the individual lines are distinguished by the eye. Such a case can be achieved for lines of thickness between 100 and 300 microns inclusive and / or spaced from 100 to 300 microns inclusive;
• When the two preceding dimensions (width of lines and space between the lines), which may be equal or different, and regular or irregular, but preferably forming a regular pattern, on the same pattern, are further reduced, for example less than or equal to at 100 μm, even less than or equal to 70 μm, or even less than or equal to 60 μm, then the eye can no longer distinguish the different individual lines and combines them, which allows to create new effects, for example to help with optical illusions. The example of figure 2 is close to this configuration since it comprises lines 100 μm wide, spaced 250 μm apart.

The second case mentioned above can advantageously be combined with particular colors to achieve surprising effects. For example, the figure 3 represents an embodiment in which the dial was first decorated by a sunburst made on a setting layer in silver, champagne or blue color (deposited by PVD or electroplating as described above). Then, decals, for example an ink of blue, red, pink or mauve color are produced. The result is a lightening of the colors on the final result, by optical effect. From a saturated ink color, it appears on the dial a pastel color, with a good depth. Thus, in this second case, the eye is deceived and perceives a color that is not really present on the dial, but which is derived from the combination of the respective colors of the decal and the color of the sunray dial.

As outstanding examples, a mauve ink decal on a silver colored layer produces a resultant pastel mauve color. A Blue ink decal on a champagne color layer produces a resulting soft green color. The figure 4 illustrates this phenomenon using a table of values corresponding to three examples. The colors are measured by the CIE Lab method, and its three parameters L *, a *, b *. In each example, the decoration method uses a surface structuring step consisting of a silver sunburst, obtained by a sunburst surface structuring step E10, carried out after a preliminary step E4 for deposition of a silver layer. . In the first case, the decal is made from a blue varnish, which allows to achieve a resulting decoration of pastel blue color. In the second case, the decal is made from a green varnish, which allows to achieve a resultant decoration of pastel green color. In the third case, the decal is made from a purple varnish, which allows to achieve a resultant decoration of mauve pastel color.

The use of the femtosecond laser is important to create a very regular pattern in the form of a very regular frame on the pad printing plate, which is necessary to obtain the effects mentioned above. In addition, the femtosecond laser allows to be very precise, to define the thickness of the engraving, the depth of the engraving, the distance between the engravings very precisely. The same method that would be implemented with a tampon printing plate formed without femtosecond laser does not achieve these optical effects and ultimately does not achieve at all a decoration with the same final appearance.

• Des motifs formés de lignes, de lignes entrecroisées, d'alternances de points et de lignes ;
• Des impressions de deux couleurs différentes, comme par exemple une ligne sur deux d'une première couleur, les autres lignes étant dans une seconde couleur ;
• Le matériau pour le cliché peut être en métal, par exemple en acier, ou en céramique, ou en verre, ou dans tout autre matériau adapté.

As mentioned above, the decoration process makes it possible to achieve a multitude of very attractive and original results, and the invention is not limited to the examples described above. As examples, it is possible to choose:

• Patterns consisting of lines, intersecting lines, alternating points and lines;
• Prints of two different colors, such as every other line of a first color, the other lines being in a second color;
• The material for the cliché may be metal, for example steel, or ceramic, or glass, or any other suitable material.

The two types of decor combined are at least partially superimposed. The impression formed by the decal defines a pattern at least partially superimposed on the surface having undergone surface structuring. The printed patterns can thus cross lines printed by the decal with streaks formed by the surface patterning.

The invention also relates to the watch element obtained by this decoration method. Such an element thus comprises relief decorations, comprising an impression obtained by pad printing superimposed on a surface patterning.

Claims (16)

Method for decorating a dial, characterized in that it comprises a step of etching (E1) a pattern on a tampon printing plate by a femtosecond laser, then that it comprises a decal step (E20) of said pattern on the dial using the pad printing plate. Method for decorating a dial according to the preceding claim, characterized in that it comprises a surface structuring step (E10) of a surface to decorate the dial and then the decal (E20) of said pattern on the dial at least partially superimposed on the surface structuring obtained in the previous step. Method for decorating a dial according to the preceding claim, characterized in that it comprises an intermediate staining step (E5) of the surface decorated or to be decorated by the surface structuring step (E10), using a color different from a color used during the decal step (E20). Method for decorating a dial according to claim 2 or 3, characterized in that the surface structuring step (E10) comprises a sunburst, or a spraying, or sanding, or beading, or the production of Côtes de Geneva, or a sniffing. Method for decorating a dial according to one of Claims 2 to 4, characterized in that the surface structuring step (E10) produces a grid of regular reliefs of mean depth less than or equal to 1 μm, or even 0, 3 μm, or even 0.1 μm. Process for decorating a dial according to one of Claims 2 to 5, characterized in that it comprises a step (E4) of deposition of a layer of metal on the surface to be decorated, in particular a malleable metal, such as silver, before the surface structuring step (E10). Method for decorating a dial according to one of Claims 2 to 6, characterized in that it comprises a staining step (E5) of the decorated surface after the surface structuring step (E10) and before the decal step (E20) by pad printing, deposition of one or more galvanic layer (s), and / or one or more PVD layer (s), and / or one or more (s) Layer (s) ALD, and / or deposition by any other technique for forming a coating that can change the perceived color of the watch element. Method for decorating a dial according to one of the preceding claims, characterized in that the etching step (E1) of a tampon printing plate produces frames comprising lines whose thickness and / or spacing is less than or equal to 150 μm, even less than or equal to 100 μm, even less than or equal to 70 μm, or even less than or equal to 60 μm. Method for decorating a dial according to one of the preceding claims, characterized in that the pattern of the tampon printing plate is such as to perceive a color of the final decoration distinct from the color of the color used in the decal step (E20). Method for decorating a dial according to one of Claims 2 to 7, characterized in that the pattern of the tampon printing plate is such that it makes it possible to perceive a color of the final decoration that is distinct from the color of the surface patterning. (E10) and the color used in the decal step (E20). Dial obtained by a decoration method according to one of the preceding claims, characterized in that it comprises a decorated surface comprising a printing by decal using a tampon printing plate formed by a femtosecond laser. Dial according to the preceding claim, characterized in that it comprises at least one surface structuring, the printing by decal being at least partially superimposed on said at least one surface structuring. Dial according to claim 11 or 12, characterized in that it comprises a printing by decal comprising lines whose thickness and / or spacing is less than or equal to 150 μm, or even less than or equal to 100 μm, or less than or equal to 70 μm, or even less than or equal to 60 μm. Dial according to claims 12 and 13, characterized in that it comprises a first color covering the surface patterning, and a superimposed decal impression in a second color distinct from the first, and in that the eye perceives a global decoration in a pastel color or a third color, distinct from the first and second colors. Dial according to one of claims 11 to 14, characterized in that it is made of metal, or ceramic, such as zirconia or alumina, or silicon, or glass, or sapphire, or nacre or material mineral. Timepiece as a watch, especially a wristwatch, characterized in that it comprises a dial according to one of claims 11 to 15.

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