The present invention is directed to a device comprising a luminescent element which is not directly visible by the user. In particular, the device is a watch or a clock, and the luminescent element is provided at a hidden face of the hands.

Background

Watches with luminescent hands are known. The luminescent hands allow to capture the daylight and to provide the residual light when the ambient light is not sufficient to read the time. Thus, the user can determine the position of the hands even in the dark, at least for a certain period of time. The hands must be provided with a phosphorescent or fluorescent coating or any phosphorescent or fluorescent element on their top face. The visual aspect of the hands is therefore restricted to the necessary phosphorescent or fluorescent coating. It is in particular not possible to design black hands, or hands having specific colours, or aesthetic aspects.

Summary

It is therefore an object of the present invention to address the above-mentioned limitations. In particular, the present invention provides a watch or any similar device comprising one or more mobile elements such as hands or discs, or any other elements the position of which varies.

These mobile elements have a top face, visible by the user, and a hidden surface, which faces a dial. Such hidden surface, or back surface is provided with an element able to emit light in such a way that it can illuminate the dial. Since the top face of the mobile element is not provided by any light emitting substance, it remains dark in absence of an external light source. Thus, the user sees the dark shape of the mobile element surrounded by the light emitted by its hidden surface.

The light is provided by any luminescent substance or material, such as a coating, a paint, a solid resin, a stick or a plate of polymer, or a flexible layer comprising at least one luminescent component, or a mixture of luminescent components. The back surface of the mobile element may be directly coated or painted, or provided with an additional element having luminescent properties, said additional element being fixed by any known mean such as glue, snaps, clips or similar tightening means. The back surface of the mobile elements may alternatively be provided with one or more sealed tube comprising a luminescent gas like tritium or equivalent. Such sealed tubes are known, and are usually made with borosilicate and filled with a substance like luminous material or Tritium or similar, also called Gaseous Tritium Light Source GTLS. They can be clipped or glued on the back surface of the mobile elements, or inserted within a recess of the back surface.

According to the present invention, the visible face of the mobile element is free of any luminescent element.

The dial can be provided with indices or other areas which can also be provided with a luminescent material, or not. Each index may be a marking made on the dial with a paint or a coating having luminescent properties. Alternatively, it can be made with a plate of polymer glued on the dial. It can further be made with a tube comprising a luminescent gas like GTLS or others. The dial of the claimed device preferably comprises a reflective area, either on part of its surface or on its entirety. A reflective area means any surface which reflects the light emitted by an external source.

The invention is described in detailed below.

Brief description of the figures

Figure 1 : example of a device comprising a luminescent material

Figure 2: Side view of the device, showing the luminescent material

Figure 3 : back view of a mobile element

Detailed description

The device (1) of the present invention comprises a dial (3) and at least one mobile element (2). The dial (3) may comprise one or more visual references, such as indices (4), which are distributed on the top face of the dial (3), in such a way to be seen by the user. The mobile element (2) moves with respect to the dial (3). In case indices are provided, they are distributed on the pathway of the mobile element (2), in such a way that the user sees the position of the mobile element (2) with respect to the indices (4). The mobile element (2) may be a hand or a disc, or any element comprising a top surface (2a), visible by the user, and a back surface (2b), which faces the dial (3). The back surface (2b) of the mobile element (2) is provided with a luminescent material (2c). A luminescent material should be understood as a material able to emit some light. It includes a temporary, as well as a permanent luminescent material. A temporary luminescent material may be any fluorescent or phosphorescent material or any similar material which emits light after having been exposed to a light source, or which exhibits some visible light when exposed to certain wavelengths. A permanent luminescent material denotes a material which intrinsically emits some light. A permanent luminescent material is also known as self-luminescent material and includes the radio luminescent materials like Tritium. Hereby the luminescent material also includes any retro-luminescent materials. A luminescent material may for example comprise phosphor, or rare-earth material or a combination thereof. The back surface (2b) of the mobile element (2) is provided with such a luminescent material (2c) either on its entire surface, or only on a portion of its surface, or on several parts of its surface.

In one embodiment, the luminescent material (2c) is a paint or a coating which comprises some luminescent components. Any kind of coating and paint may be used, independently on their process of application. The coating may for instance comprise a chemical material which is polymerized under UV or under high temperature.

In another embodiment, the luminescent material (2c) is a solid element which is tightened onto the back surface (2b) of the mobile element (2). Any tightening means like glue, clips, snaps or equivalent may be used. Such a solid element can be a flat element such as a resin stick, or a polymer material comprising luminescent components. The solid element may alternatively be a tube filed with a luminescent material. In that case, it is preferably a sealed tube comprising a luminescent gas such as tritium or any other gas able to provide some light. In case the luminescent material is a tube, it can be inserted in a recess provided in the back surface (2c) of the mobile element (2). It is also contemplated that more than one tube is combined to the mobile element (2). The above configuration allows to design a mobile element (2) having luminescent properties while the top surface (2a) remains free of any luminescent material. The top surface (2a) may be for example black, and without any luminescent properties. Being provided by the luminescent material, the back surface (2b) of the mobile element (2) provides some light in the direction of the dial (3). In absence of an external light source, the user can therefore determine the position of the mobile element (2) with regard to the dial (3), which corresponds to the non-illuminated part surrounded by the light emitted by the luminescent material and reflected by the dial (3).

While not mandatory, it is preferable that the dial (3) is a reflective surface. In this way, the light emitted by the back surface (2b) of the mobile element (2) is better reflected toward the user. Thus, the surface of the dial (3) is preferably slick and non-rough. It is also preferably not black or dark coloured.

In another aspect, the dial (3) reflects the ambient light toward the luminescent surface (2b) of the mobile element (2). In case the luminescent material provides light after being activated by an external source of light, it is advantageous that the dial (3) reflects the light in an efficient way in order to better illuminate the hidden face (2b) of the mobile element (2). The dial (3) is therefore preferably well reflecting material or even a mirror. Reflecting dial is preferred for temporarily luminescent materials, and optional for gas tubes, or any other self-luminescent material.

The indices (4) may also be provided by a luminescent material, either permanently or temporarily luminescent. The indices (4) may be of the same luminescent material as the back surface (2b) of the mobile element (2), or of another luminescent material.

The device (1) of the present invention is preferably a watch or a clock or any other instrument, comprising one or two hands, each hand rotating around a central axis, and a dial (3), wherein the back surface (2b) of both hands is provided with a luminescent material, as described above, in such a way that the relative position of the hands can be determined in absence of external source of light. In a preferred embodiment, the dial (3) is provided with one or several indices (4) provided with a luminescent material, in such a way that in absence of external light source, the position of the hands relative to the indices (4) can be determined.