EP3602205B1 - Skeleton watch with photochromic dial - Google Patents

Description

Field of the invention

The invention relates to a watch, in particular a so-called skeleton watch.

Background of the invention

In the skeleton watches of the prior art, the watch face can be omitted, made of a transparent material or in a perforated plate so as to reveal the watch movement behind the dial.

Such watches are aesthetic, but when the light is high, the time is difficult to read because the hands have little contrast compared to the watch movement.

Also, it is difficult to have a readable logo on a skeleton watch, especially when the light is high.

Watches are also known, as disclosed in JP 3 140649 U , the dial elements of which consist of a photochromic plate so that these elements become colored when the dial is exposed to a quantity of UV rays greater than a threshold value.

Summary of the invention

The invention aims to remedy the drawbacks of the state of the art by providing a watch, in particular a skeleton watch making it possible to read the time and any logo more easily regardless of the light conditions.

• le mouvement horloger soit apparent lorsque la plaque photochromique est exposée à une quantité de rayons UV inférieure à une première valeur seuil ;
• le mouvement horloger soit masqué lorsque la plaque photochromique est exposée à une quantité de rayons UV supérieure à une deuxième valeur seuil.

To do this, is proposed according to a first aspect of the invention, a watch, comprising a watch movement housed in a watch case formed by a middle part, closed by a crystal and a back, the watch movement being arranged to drive in rotation of at least one hand, the watch movement being covered by a dial visible through the crystal, the dial being disposed between the watch movement and said at least one hand, the watch being characterized in that the crystal is transparent to UV rays and in that the dial is made of a photochromic plate so that:

• the watch movement is visible when the photochromic plate is exposed to an amount of UV rays less than a first threshold value;
• the watch movement is masked when the photochromic plate is exposed to a quantity of UV rays greater than a second threshold value.

In fact, the photochromic plate darkens under the effect of U.V. radiation and it becomes clearer under the effect of ambient heat, in an indefinitely reversible manner. Thus, when the watch is not exposed to UV radiation, typically when the watch is worn indoors, the watch movement is visible behind the dial because the photochromic plate is transparent to the visible spectrum. On the contrary, when the photochromic plate is exposed to UV rays, the dial darkens. The more the face of the watch is exposed to a significant amount of UV rays, the more it darkens until it becomes opaque, which allows the hands to appear clearly in contrast to the opaque dial of the watch.

The first threshold value and the second threshold value depend on the material or materials chosen for the photochromic plate.

• la plaque photochromique peut être une plaque d'un matériau transparent aux rayons UV comportant dans sa masse des inclusions de matières photochromiques ;
• la plaque photochromique peut être une plaque d'un matériau transparent revêtu par une couche photochromique sous la forme d'un film polymère incluant de la matière photochromique ou d'un peinture incluant des pigments de matière photochromique ;

• le matériau transparent aux rayons UV peut être un verre minéral ;
• le matériau transparent aux rayons UV peut être un verre organique ;
• le matériau transparent peut être une résine organique, typiquement une résine acrylique ou une résine polycarbonate transparente au rayonnement UV ;
• les inclusions photochromiques peuvent être, de préférence dans le cas de verres minéraux, des inclusions d'un composé d'halogénure d'argent et/ou de bromure d'argent ;
• les inclusions photochromiques peuvent être de préférence dans le cas de verres organiques, typiquement en résine synthétique de préférence en résine acrylique ou en résine polycarbonate des inclusions de molécules d'oxazines et/ou de de composés de de naphtopyrane.
• la plaque photosensible peut comporter une inscription imprimée ou gravée sur au moins une de ces faces ;
• le cadran peut présenter une teinte noire lorsque la plaque photochromique est exposée à une quantité de rayons UV supérieure à la deuxième valeur seuil, de façon à rendre l'heure plus lisible ;
• la ou les aiguille(s) peut (peuvent) être blanche(s) de façon à être plus visible(s) lorsque le cadran s'obscurcit.

The watch according to the first aspect of the invention can also have one or more of the following characteristics taken individually or according to any technically possible combination:

• the photochromic plate may be a plate of a material transparent to UV rays comprising in its mass inclusions of photochromic materials;
• the photochromic plate may be a plate of a transparent material coated with a photochromic layer in the form of a film polymer including photochromic material or a paint including pigments of photochromic material;

• the material transparent to UV rays may be a mineral glass;
• the material transparent to UV rays may be an organic glass;
• the transparent material may be an organic resin, typically an acrylic resin or a polycarbonate resin transparent to UV radiation;
• the photochromic inclusions may be, preferably in the case of inorganic glasses, inclusions of a silver halide and / or silver bromide compound;
• the photochromic inclusions can preferably be in the case of organic glasses, typically in synthetic resin, preferably in acrylic resin or in polycarbonate resin, inclusions of oxazine molecules and / or of naphthopyran compounds.
• the photosensitive plate may include an inscription printed or engraved on at least one of these faces;
• the dial may have a black tint when the photochromic plate is exposed to an amount of UV rays greater than the second threshold value, so as to make the time more readable;
• the needle (s) can be white so as to be more visible when the dial darkens.

Brief description of the drawings

• la figure 1 représente une vue schématique en demi-coupe d'une montre selon un mode de réalisation de l'invention ;
• la figure 2 représente une vue schématique de dessus de la montre de la figure 1 lorsqu'elle est exposée à une quantité d'UV inférieure à une première valeur seuil ;
• la figure 3 représente une vue schématique de dessus de la montre de la figure 1 lorsqu'elle est exposée à une quantité d'UV comprise entre la première valeur seuil et une deuxième valeur seuil ;
• la figure 4 représente une vue schématique de dessus de la montre de la figure 1 lorsqu'elle est exposée à une quantité d'UV supérieure à la deuxième valeur seuil.

Other features and advantages will emerge clearly from the description which is given below, by way of indication and in no way limiting, with reference to the appended drawings, in which:

• the figure 1 represents a schematic half-section view of a watch according to one embodiment of the invention;
• the figure 2 represents a schematic view from above of the watch of the figure 1 when exposed to an amount of UV less than a first threshold value;
• the figure 3 represents a schematic view from above of the watch of the figure 1 when it is exposed to an amount of UV between the first threshold value and a second threshold value;
• the figure 4 represents a schematic view from above of the watch of the figure 1 when exposed to an amount of UV greater than the second threshold value.

Detailed description of an embodiment

A watch 1 according to one embodiment of the invention will now be described with reference to figures 1 to 4 .

This watch 1 comprises a watch case 2 which contains a watch movement 3. The case 2 comprises a caseband 2a, a first and a second closing element of the case, respectively a crystal 5 and a back F. The caseband 16 is provided with of four strap fixing lugs B. The back F is fixed to the caseband 2a by means of screws not shown in the drawing and the crystal 5 is conventionally driven into a recess in the caseband with the interposition of a seal. The ice is made of a material transparent to UV rays.

The watch movement 3 makes it possible to rotate the hands 4. The watch 1 also comprises a dial 5. The dial 5 closes the watch case 2. The dial 5 is placed directly above the watch movement 3. The dial 5 is therefore interposed between the watch movement 3 and the hands 4.

The hands 4 preferably have a light shade, typically white, so as to be more visible on the dial.

The dial 5 is formed by a photochromic plate 6 arranged directly above the watch movement 3 and directly below the hands 4. The photochromic plate 6 comprises a plate of a transparent material in which are included photochromic substances or which is coated with a coating containing photochromic substances.

The photochromic plate 6 darkens under the effect of UV radiation and it becomes clearer under the effect of ambient heat, in an indefinitely reversible manner. This phenomenon is obtained by the activation of molecules of photochromic substances. The absorption of the photochromic plate is determined at all times by the balance between the number of photosensitive molecules activated by UV stimulation and the number of molecules deactivated by heat.

According to one embodiment, the photochromic plate 6 is formed from a synthetic resin, preferably a polycarbonate resin or an acrylic resin transparent to UV rays, in which molecules of oxazines and / or naphthopyran compounds are dispersed in the mass. Typically the thickness of the plate is of the order of 0.85 mm.

According to one variant, the photochromic plate is a plate of a material transparent to radiation coated with a photochromic layer in the form of a polymer film including photochromic material identical to that described in the above paragraph.

The phenomenon of darkening and lightening of this type of plaque is well known and results respectively from the breaking under the effect of UV rays of the molecules of oxazines and / or of naphthopyran compounds and from their reconstitution when the 'UV is gone.

According to another variant, the photochromic plate is a mineral glass in which the photochromic inclusions are inclusions of a compound of silver halide and / or of silver bromide. In this case, under UV exposure, the silver - halide / bromide bonds break and the silver atoms join together which darkens the plate. The silver - halide bonds are reconstituted as soon as the UV exposure is stopped, restoring its clarity to the plate.

Furthermore, an inscription 7 can be engraved or printed on the dial.

The figures 2 to 4 represent the evolution of the color of the dial 5 as a function of its exposure to UV rays.

So the figure 2 represents the watch when it is not exposed to UV rays. As can be seen in this figure, the dial is then transparent so that the watch movement is visible through the dial.

The figure 3 represents the watch when it is exposed to a low amount of UV. This quantity of UV is typically between the first threshold value and the second threshold value. In this case, the dial is partially obscured, so that the watch movement is partially visible through the dial. In addition, the hands 4 and the inscription 7 begin to stand out in contrast so as to be readable despite the increase in brightness. Indeed, the darkening of the dial makes it possible to limit the reflections associated with the watch movement.

The figure 4 represents the watch when it is exposed to an amount of UV greater than the second threshold amount. In this case, the dial has taken on a dark shade so that it completely obscures the watch movement. The hands 4 and the inscription 7 are then very visible, despite a strong light.

Naturally, the invention is not limited to the embodiments described with reference to the figures and variants could be envisaged without departing from the scope of the invention. Thus, indexes could for example be engraved or printed on the photochromic plate, which would make it possible to have a skeleton watch with visible indexes while dispensing with the flange. The dial could also have other shapes than that shown.

Claims (9)

1. Watch (1) comprising a horological movement (3) housed in a watch case (2) formed by a middle part, a crystal and a bottom, the horological movement (3) being arranged to rotate at least one hand (4), the horological movement (3) being covered by a dial (5) visible through the crystal, the dial (5) being disposed between the horological movement (3) and said at least one hand (4), said watch being characterised in that the crystal is transparent to UV rays and in that the dial (5) consists of a photochromic plate (6) so that:

   - the horological movement (3) is visible when the photochromic plate (6) is exposed to an amount of UV radiation below a first threshold value,

   - the horological movement (3) is masked when the photochromic plate (6) is exposed to an amount of UV radiation above a second threshold value.
2. Watch (1) according to claim 1, wherein the photochromic plate (6) is a plate made from a material transparent to UV rays comprising within said material inclusions of photochromic materials.
3. Watch (1) according to claim 1, wherein the photochromic plate (6) is a plate made from a transparent material coated with a photochromic layer in the form of a polymer film including photochromic material.
4. Watch (1) according to either claim 2 or 3, wherein the material transparent to UV rays is a mineral glass.
5. Watch (1) according to either claim 2 or 3, wherein the material transparent to UV rays is an organic glass.
6. Watch (1) according to claim 5, wherein the transparent material is a synthetic resin, preferably a polycarbonate resin or an acrylic resin transparent to UV rays.
7. Watch (1) according to claim 2 and claim 4, wherein the photochromic inclusions are inclusions of a silver halide and/or silver bromide compound.
8. Watch (1) according to claim 2 or 3 and claim 5, wherein the photochromic inclusions are inclusions of oxazine molecules and/or of naphthopyrane compounds.
9. Watch (1) according to any of the preceding claims, wherein the photosensitive plate (6) comprises an inscription printed or etched on at least one of these faces.

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