EP3671365B1 - Timepiece dial - Google Patents

Description

Scope of the invention

The invention relates to a dial comprising a support, a mother-of-pearl sheet having a front and a back and at least partially covering the support, and at least one decorative element on the back, said decorative element being arranged to be visible on the front of the mother-of-pearl sheet under the effect of a stimulus and invisible on the front of the mother-of-pearl sheet in the absence of said stimulus, said decorative element defining around itself, on the back of the mother-of-pearl sheet, at least a first empty area and at least a second empty area on the front of the mother-of-pearl sheet, opposite the first empty area. The present invention also relates to a timepiece comprising such a dial.

Background of the invention

The use of mother-of-pearl for dial making is already well-established in the watchmaking industry for its distinctive aesthetic. Mother-of-pearl has a biological origin, iridescent reflections, and translucency that make each piece unique. Depending on its origin, mother-of-pearl can have various intrinsic hues (e.g., white, gray, pink, green). To alter its appearance, mother-of-pearl can be colored by immersion in a dye bath. A design can also be applied to the obverse (the side visible to the wearer of the timepiece) or the reverse (the back side, facing the inside of the timepiece) of the mother-of-pearl, the latter option relying on the material's translucency properties. The visible design can consist of a colored lacquer or a metallic coating. The lacquer can be applied using techniques commonly employed for lacquering, such as spraying, pad printing, or screen printing. A metallic coating can It can also be applied using physical vapor deposition techniques such as PVD. Other inorganic layers, such as nitrides, carbides, or oxides, can be applied by PVD or CVD.

Depending on its thickness on the obverse of the piece, the decoration can even cover and obscure the unique shape of the mother-of-pearl. In these techniques, the decoration, even when placed on the reverse side of the mother-of-pearl dial, is always visible on the final piece.

The patent EP 1672436 mentions, for example, the manufacture of a mother-of-pearl dial with a uniform metallic appearance by depositing a metallic coating over the entire surface of the front of the dial.

The patent CH 559 924 It describes a dial comprising a mother-of-pearl disc beneath which are placed luminescent elements visible at night and invisible during the day, so as not to be detected by the eye through the mother-of-pearl disc. In this document, the luminescent material is applied uniformly to the reverse of the coin and does not allow for the appearance of a complex design on the obverse of the mother-of-pearl.

The patent CH 697 210 This describes a dial comprising a sheet of mother-of-pearl whose reverse side has cavities filled with phosphorescent pigments. These cavities reveal a design visible in the dark beneath the mother-of-pearl, the design and intensity of which can be chosen according to the shape and depth of the cavities. However, the intensity of the design in the dark must be limited to ensure that the phosphorescent pigments remain invisible on the obverse of the dial when it is exposed to daylight.

Summary of the invention

The present invention aims to remedy these drawbacks by proposing a mother-of-pearl dial for a watch part, comprising a decoration on the reverse of the part, the decoration of which only becomes visible on the obverse. the piece that under the effect of an external or internal stimulus, luminous, electrical, or physical, for which the invisible character of said decoration on the front of the piece, when it is not under the effect of its stimulus, has been improved.

The present invention also aims to provide a mother-of-pearl dial for a watch part comprising several decorations on the reverse of the part, visible on the front of the part with different light intensities when they are under the effect of their stimulus, all the decorations being invisible on the front of the part when they are not under the effect of their stimulus.

For this purpose, the invention relates to a dial as defined in claim 1 of the patent.

According to the invention, the dial comprises at least one color compensation layer deposited on at least one of the first and second empty areas, the color of said color compensation layer being chosen such that the color difference ΔE in the CIE Lab color space between the color of the color compensation layer and the color of the decorative element in the absence of said stimulus, perceived by a user looking at the front of the mother-of-pearl sheet, is less than 3, preferably less than or equal to 1.

Thus, thanks to the color compensation layer, the invisibility of the design on the coin's front is improved when it is not under the influence of its stimulus. It is then possible to use a design with a higher light intensity when it is under the influence of its stimulus, or several designs producing different light intensities, some of which can be high, without the risk of it appearing on the coin's front when the stimulus is not applied.

The present invention also relates to a timepiece comprising such a dial.

Brief description of the drawings

• les figures 1 à 3 sont des vues schématisées de différents modes de réalisation d'un cadran selon la présente invention.

Other features and advantages of the invention will become clearer upon reading the following description of various embodiments of the invention, given by way of simple illustrative and non-limiting examples, and the accompanying figures, among which:

• THE figures 1 to 3 are schematic views of different embodiments of a dial according to the present invention.

Detailed description of preferred embodiments

The present invention relates to a clock dial, comprising a support, a mother-of-pearl sheet having an obverse and a reverse and covering at least partially the support, and at least one decorative element provided on the reverse side, between the support and the mother-of-pearl sheet.

The support is preferably metallic. It can be made of brass, gold-based (yellow or white), silver, or any other suitable metal. It can be attached to the mother-of-pearl sheet bearing the decorative element by plating, gluing, or any other appropriate means.

The decorative element is arranged to be visible on the front of the mother-of-pearl sheet under the effect of a stimulus and invisible on the front of the mother-of-pearl sheet in the absence of said stimulus.

The decorative element defines around itself, on the reverse side of the mother-of-pearl sheet, at least one first empty area, that is to say, an area on the reverse side of the mother-of-pearl not occupied by said decorative element. The decorative element also defines, by projection onto the obverse side of the mother-of-pearl sheet, opposite the first empty area, at least one second empty area, that is to say, an area on the obverse side of the mother-of-pearl through which said decorative element, on the reverse side, does not appear.

According to the invention, the dial comprises at least one color compensation layer deposited on at least one of the first and second empty areas, the color of said color compensation layer being chosen so that the color difference ΔE in the CIE Lab color space between the colors of the color compensation layer and the decorative element in the absence of said stimulus, perceived by a user looking at the front of the mother-of-pearl sheet, is less than 3, preferably less than or equal to 1.

The color difference ΔE in the CIE Lab color space is defined as a measure of the difference between two colors by equation (I): $$\mathrm{\Delta }{E}^{\ast }=\sqrt{{\left(L_2^{\ast }-L_1^{\ast }\right)}^2+{\left(a_2^{\ast }-a_1^{\ast }\right)}^2+{\left(b_2^{\ast }-b_1^{\ast }\right)}^2}$$ $L_1^{\ast },a_1^{\ast },b_1^{\ast }$ are the coordinates in the CIE Lab color space of the first color to be compared and $L_2^{\ast },a_2^{\ast },b_2^{\ast }$ are the coordinates in the CIE Lab color space of the second color to be compared.

The decorative element includes stimulus-reactive particles, namely phosphorescent or photochromic particles to be sensitive to a light stimulus, electro-chromic particles to be sensitive to an electrical stimulus, or thermochromic particles to be sensitive to a temperature variation.

Preferably, the decorative element is obtained from a reactive lacquer or ink containing an epoxy or polyurethane binder, to which the reactive particles are added. The size of the reactive particles can range from 0.5 µm to 100 µm, and preferably from 10 µm to 50 µm. Inorganic or organic additives can be used to modify the tint of the reactive lacquer and achieve the desired color if necessary, as well as its texture or optical properties. The tint of the reactive lacquer or ink is chosen so that the decorative element, when not under the effect of its stimulus, modifies the intrinsic appearance of the mother-of-pearl leaf as little as possible, and becomes completely invisible on the front of the dial with the help of the color compensation layer.

The decorative element is placed between the support and the mother-of-pearl sheet. For this purpose, the decorative element can be formed on the reverse side of the mother-of-pearl sheet, either directly on the surface of the reverse side of the mother-of-pearl, or in at least one blind cavity formed from the reverse side of the mother-of-pearl and arranged to receive said decorative element.

Advantageously, the reverse side of the mother-of-pearl sheet can have several blind cavities to form several decorative elements.

These blind cavities are created from the reverse side of the mother-of-pearl sheet using laser, mechanical, or manual engraving. The geometries and depths of these blind cavities are precisely controlled according to the decorative element to be represented and the intensity of that element as it appears through the mother-of-pearl sheet under the influence of a stimulus. The blind cavities are then selectively filled with reactive lacquer. The blind cavities allow for the use of a larger quantity of reactive lacquer, thus increasing the intensity of the optical effects. Furthermore, and advantageously, the blind cavities have varying depths, enabling the creation of multiple decorative elements that, under the influence of the stimulus, will appear with varying intensities, creating contrasts in color.

The decorative element can also be placed on the support which will then be applied against the reverse of the mother-of-pearl, by plating or gluing for example.

Lacquer or reactive ink is selectively applied to create a design on the reverse side of the mother-of-pearl sheet or support. The processes that The following methods can be implemented for this purpose: lacquering or spraying using a mask or photosensitive lacquer to selectively deposit the lacquer, selective laser or mechanical ablation of the lacquer, screen printing, pad printing or any other suitable printing technique.

The composition and thickness of the color compensation layer used in the present invention are adapted according to the composition of the reactive lacquer or ink, the thickness of the mother-of-pearl sheet and its color, in order to obtain a compensation layer whose color allows to satisfy equation (I).

The color compensation layer can be of an organic nature, such as a varnish comprising pigments or dyes to obtain the color necessary to satisfy equation (I).

The color compensation layer can be inorganic in nature, for example based on oxides or nitrides such as zirconium or titanium or based on metals such as for example aluminium, silver or gold alloy having the colour necessary to satisfy equation (I).

Advantageously, the compensation layer is transparent, especially when the compensation layer is applied to the reverse side of the mother-of-pearl sheet.

In addition, the color compensation layer deposited on the first empty area can also be metallic, intrinsically exhibiting the color necessary to satisfy equation (I).

The color compensation layer can be applied by spraying, dip coating, pad printing, screen printing, sol-gel, printing or by vacuum techniques such as PVD.

According to one embodiment of the invention, the surface of at least one of the first and second empty zones may be diffusive. The diffusive surface may The design can be created on the reverse and/or obverse of the mother-of-pearl sheet by chemical, laser, or mechanical engraving. Another variation is the use of a diffusive film applied to the surface of the mother-of-pearl, preferably on the reverse side of the sheet.

According to a first embodiment of the invention shown in the figure 1 The dial 1 comprises a support 2, a mother-of-pearl sheet 4 having an obverse and a reverse, and several decorative elements 6 arranged directly on the reverse of the mother-of-pearl sheet 4 to form an image that appears through the obverse of the mother-of-pearl sheet 4 when the decorative elements 6 are subjected to their stimulus. The mother-of-pearl sheet 4 and the decorative elements 6 are assembled on the support 2 by means of a layer of glue 8. The decorative elements 6 define around themselves, on the reverse of the mother-of-pearl sheet 4, first empty areas 10, and, on the obverse of the mother-of-pearl sheet 4, opposite the first empty areas 10, second empty areas 12.

In this embodiment, the color compensation layer 14 according to the invention is provided on the reverse side of the mother-of-pearl sheet 4 only in the first empty areas 10 around the decorative elements 6. Thus, thanks to the color compensation layer 14 according to the invention, a user 16 looking at the front of the mother-of-pearl sheet 4 does not perceive any color difference between the color, through the mother-of-pearl sheet 4, of the decorative elements 6 not subjected to their stimulus and the color of the color compensation layer 14 deposited in the first empty areas 10 and which appears through the second empty areas 12. The decorative elements 6 not subjected to their stimulus are totally invisible.

When subjected to their stimulus, the color of the decorative elements changes so that they become visible on the front of the dial, through the mother-of-pearl sheet, in relation to the color compensation layer, which is then no longer operational.

According to another embodiment shown in the figure 2 , the color compensation layer 14 is planned on the reverse side of the sheet of mother-of-pearl only on the second empty areas 12 opposite the first empty areas 10. As in the previous variant, the mother-of-pearl sheet 4 and the decorative elements 6 are assembled to the support 2 by a layer of glue 8.

Thus, thanks to the color compensation layer 14 according to the invention, a user 16 looking at the front of the mother-of-pearl sheet 4 does not perceive any color difference between the color, through the mother-of-pearl sheet 4, of the decorative elements 6 not subjected to their stimulus and the color of the color compensation layer 14 deposited on the second empty areas 12. The decorative elements 6 not subjected to their stimulus are totally invisible.

When subjected to their stimulus, the color of the decorative elements changes so that they become visible on the front of the dial, through the mother-of-pearl sheet, in relation to the color compensation layer, which is then no longer operational.

According to another embodiment shown in the figure 3 , the reverse of the mother-of-pearl sheet 4 includes blind cavities 16 filled with reactive lacquer to form the decorative elements 6.

In this embodiment, the color compensation layer 14 according to the invention is provided on the reverse side of the mother-of-pearl sheet 4 only in the first empty areas 10 around the decorative elements 6, as in the embodiment of the figure 1 .

According to another variant of the invention, the front of the mother-of-pearl sheet 4 may further include a diffusive surface 18 over the whole surface or only on the surface of the second empty zones 12 opposite the first empty zones 10 occupied by the color compensation layer 14 or only on the surface opposite the decorative elements 6.

Thus, thanks to the color compensation layer, the invisible nature of the decoration on the obverse of the coin, when it is not under the effect of its stimulus, is improved. It is then possible to use a decoration with a higher light intensity when it is under the effect of its stimulus, or several decorations giving different light intensities, some of which can be high, without risk of it or them appearing on the back of the piece when the stimulus is not applied.

Claims (14)

1. A dial (1) comprising a support (2), a mother-of-pearl leaf (4) with an obverse and a reverse side and at least partially covering the support (2), and at least one decorative element (6) provided on the reverse side of said mother-of-pearl leaf (4), said decorative element (6) being arranged to be visible on the obverse of the mother-of-pearl leaf (4) when exposed to a stimulus and invisible on the obverse of the mother-of-pearl leaf (4) in the absence of said stimulus, characterised in that said decorative element (6) defines around it, on the reverse side of the mother-of-pearl leaf (4), at least a first empty zone (10) which is a zone that is not occupied by the decorative element, and at least a second empty zone (12) which is a zone on the obverse of the mother-of-pearl through which the reverse side of the decorative element does not appear, facing said first empty zone (10), said dial (1) comprising at least one colour compensation layer (14) deposited on at least one of the first empty zone (10) and second empty zone (12), the colour of said colour compensation layer (14) being selected such that the difference in colour ΔE in the CIE Lab colour space between the colour compensation layer and the decorative element in the absence of said stimulus, perceived by a user looking at the obverse of the mother-of-pearl leaf, is less than 3, preferably less than or equal to 1, and in that the surface of the compensation layer facing the support is coplanar with the surface of the decorative element facing the support.
2. The dial according to claim 1, characterised in that the colour compensation layer is provided on the reverse side of the mother-of-pearl leaf only on the first empty zone around the decorative element.
3. The dial according to claim 1, characterised in that the colour compensation layer is provided over the entire reverse surface of the mother-of-pearl leaf.
4. The dial according to any of the preceding claims, characterised in that the colour compensation layer is provided on the obverse of the mother-of-pearl leaf only on the second empty zone.
5. The dial according to any of claims 1 to 3, characterised in that the colour compensation layer is provided over the entire obverse surface of the mother-of-pearl leaf.
6. The dial according to any of the preceding claims, characterised in that the colour compensation layer is organic or inorganic in nature, or a combination of both.
7. The dial according to claim 6, characterised in that the colour compensation layer deposited on the first empty zone is metallic.
8. The dial according to any of the preceding claims, characterised in that the surface of at least one of the first and second empty zones is diffusive, said at least one of the surfaces being arranged on the obverse or on the reverse side.
9. The dial according to any of the preceding claims, characterised in that the reverse side of the mother-of-pearl leaf comprises at least one blind cavity holding the decorative element.
10. The dial according to claim 9, characterised in that the reverse side of the mother-of-pearl leaf comprises several blind cavities of different depths in order to hold several decorative elements which, when exposed to the stimulus, appear with different intensities.
11. The dial according to any of claims 1 to 8, characterised in that the decorative element is arranged on the support.
12. The dial according to claim 11, characterised in that it comprises a corresponding engraving on the reverse side.
13. The dial according to any of the preceding claims, characterised in that the decorative element comprises phosphorescent or photochromic particles so as to be sensitive to a luminous stimulus, electrochromic particles so as to be sensitive to an electrical stimulus, or thermochromic particles so as to be sensitive to a temperature variation.
14. A timepiece comprising a dial according to any of claims 1 to 12.