WATCH

Abstract

A skeleton watch includes a horological movement housed in a watch case, the horological movement being arranged to rotate at least one hand, the horological movement being covered by a dial, and the dial being disposed between the horological movement and the at least one hand. The dial includes a photochromic plate so that the horological movement is visible when the photochromic plate is exposed to an amount of UV radiation below a first threshold value and the horological movement is masked when the photochromic plate is exposed to an amount of UV radiation above a second threshold value.

Claims

1-9. (canceled)

10. A watch comprising: a horological movement housed in a watch case formed by a middle part, a crystal and a bottom, the horological movement being arranged to rotate at least one hand, the horological movement being covered by a dial visible through the crystal, the dial being disposed between the horological movement and said at least one hand, wherein the crystal is transparent to UV rays and the dial includes a photochromic plate so that: the horological movement is visible when the photochromic plate is exposed to an amount of UV radiation below a first threshold value, and the horological movement is masked when the photochromic plate is exposed to an amount of UV radiation above a second threshold value.

11. The watch according to claim 10, wherein the photochromic plate is a plate made from a material transparent to UV rays comprising within said material inclusions of photochromic materials.

12. The watch according to claim 10, wherein the photochromic plate is a plate made from a transparent material coated with a photochromic layer in the form of a polymer film including photochromic material.

13. The watch according to claim 11, wherein the material transparent to UV rays is a mineral glass.

14. The watch according to claim 11, wherein the material transparent to UV rays is an organic glass.

15. The watch according to claim 14, wherein the transparent material is a synthetic resin, preferably a polycarbonate resin or an acrylic resin transparent to UV rays.

16. The watch according to claim 14, wherein the transparent material is a polycarbonate resin or an acrylic resin transparent to UV rays.

17. The watch according to claim 11, wherein the photochromic inclusions are inclusions of a silver halide and/or silver bromide compound.

18. The watch according to claim 11, wherein the photochromic inclusions are inclusions of oxazine molecules and/or of naphthopyrane compounds.

19. The watch according to claim 10, wherein the photosensitive plate comprises an inscription printed or etched on at least one face.

Description

SUMMARY DESCRIPTION OF THE DRAWINGS

[0022] Other particularities and advantages will emerge clearly from the description that is given thereof below, by way of indication and in no way limitatively, with reference to the accompanying drawings, in which:

[0023] FIG. 1 shows a schematic view in half-section of a watch according to one embodiment of the invention;

[0024] FIG. 2 shows a schematic plan view of the watch in FIG. 1 when it is exposed to an amount of UV below a first threshold value;

[0025] FIG. 3 shows a schematic plan view of the watch of FIG. 1 when it is exposed to an amount of UV lying between the first threshold value and the second threshold value;

[0026] FIG. 4 shows a schematic plan view of the watch in FIG. 1 when it is exposed to an amount of UV above the second threshold value.

DETAILED DESCRIPTION OF AN EMBODIMENT

[0027] A watch 1 according to an embodiment of the invention will now be described with reference to FIGS. 1 to 4.

[0028] This watch 1 comprises a watch case 2 that contains a horological movement 3. The case 2 comprises a middle part 2a, and a first and second element closing the case, respectively a crystal 5 and a bottom F. The middle part 16 is provided with four horns for fixing the bracelet B. The bottom F is fixed to the middle part 2a by means of screws, not shown in the drawing, and the crystal 5 is conventionally wedged in a recess in the middle part with the interposing of a seal. The crystal is produced from a material transparent to UV rays.

[0029] The horological movement 3 rotates the hands 4. The watch 1 also comprises a dial 5. The dial 5 closes the watch case 2. The dial 5 is disposed directly above the horological movement 3. The dial 5 is therefore interposed between the horological movement 3 and the hands 4.

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

[0030] The dial 5 is formed by a photochromic plate 6 disposed directly above the horological movement 3 and directly below the hands 4. The photochromic plate 6 comprises a plate made from a transparent material in which photochromic substances are included or which is coated with a coating containing photochromic substances.

[0031] The photochromic plate 6 darkens under the effect of UV radiation and lightens under the effect of ambient heat, and this in an indefinitely reversible manner. This phenomenon is obtained by activation of molecules of photochromic substances. The absorption of the photochromic plate is determined at any moment by equilibrium between the number of photosensitive molecules activated by the UV stimulation and the number of molecules deactivated by heat.

[0032] According to one embodiment, the photochromic plate 6 is formed by a synthetic resin, preferably a polycarbonate resin or an acrylic resin transparent to UV radiation, in which molecules of oxazines and/or naphthopyrane compounds are dispersed within the resin. Typically the thickness of the plate is around 0.85 mm.

[0033] According to one variant, the photochromic plate is a plate made from 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 paragraph above.

[0034] The phenomenon of darkening and lightening of this type of plate is well known and results respectively from the rupturing of the molecules of oxazines and/or naphthopyrane compounds under the effect of UV rays and reconstitution thereof when the UV has disappeared.

[0035] According to another variant, the photochromic plate is a mineral glass in which the photochromic inclusions are inclusions of a silver halide and/or silver bromide compound. In this case, under exposure to UV, the silver-halide/bromide bonds rupture and the silver atoms combine with each other, which darkens the plate. The silver-halide bonds are reconstituted as soon as exposure to UV stops, giving clarity to the plate again.

[0036] Moreover, an inscription 7 may be etched or printed on the dial.

[0037] FIGS. 2 to 4 show the change in the colour of the dial 5 according to the exposure thereof to UV rays.

[0038] Thus FIG. 2 shows 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 horological movement is visible through the dial.

[0039] FIG. 3 shows the watch when it is exposed to a small amount of UV. This amount of UV is typically between the first threshold value and the second threshold value. In this case, the dial is partially darkened, so that the horological movement is partially visible through the dial. Furthermore, the hands 4 and the inscription 7 begin to appear by contrast so as to be legible despite the increase in brightness. This is because the darkening of the dial limits the reflections related to the horological movement.

[0040] FIG. 4 shows the watch when it is exposed to an amount of UV greater than the second threshold amount. In this case, the dial has adopted a dark colour so that it completely masks the horological movement. The hands 4 and the inscription 7 are then highly visible, despite high brightness.

[0041] 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 indices could for example be etched or printed on the photochromic plate, which would make it possible to have a skeleton watch with visible indices while dispensing with any highlight. The dial could also have forms other than that shown.