CH717749B1 - Technical or decorative part combining a transparent material and an amorphous silica-based material and its manufacturing process. - Google Patents

Abstract

A transparent substrate (10) made of a transparent material resistant to a temperature greater than 500°C, such as sapphire, has near its edge a groove (15) machined in its thickness and lined with an enamel deposit (25) opaque, translucent or transparent, colored or not, depending on the pigments used in the composition of the enamel. Application to the dial of a timepiece.

Description

TECHNICAL AREA

The present invention relates to a technical or decorative piece combining a transparent material resistant to a temperature above 500 ° C and a silica-based material. It relates more particularly to such a part comprising an enamel deposit at least in its thickness. The invention will be illustrated by way of example by the dial of a timepiece whose aesthetic appearance can be modified, and/or which can be structured to make visible parts of the movement or information displayed under the dial. .

TECHNOLOGICAL BACKGROUND

[0002] Watches with mechanical movements, known as "skeleton watches", have been known for a long time. A Swiss patent CH 28539 describes a watch in which the dial is made of a transparent material such as glass, mica, or celluloid and allows the mechanism of the movement, and the metal plates and bridges, to be seen. The hour markers are attached by any means to the visible surface of the dial. US patents 4,534,660 and CH 690,518 describe even more "skeleton" watches. In US Pat. No. 4,534,660, the top plate forming the crystal, the plates and the bridges, and the bottom plate constitute a stack made of a crystalline material such as sapphire, said plates being machined with openings or recesses to accommodate the parts of the movement, so as to make the entire mechanism of the watch visible. Patent CH 690 518 has the same aim, but with a one-piece transparent mounting cage produced by ultrasonic machining using a sonotrode. In this last document it is advisable to transfer the hour markers to the bezel to increase the aesthetic effect.

[0003] Between the oldest prior art where the dial is entirely opaque and the aforementioned prior art where it is entirely transparent, with the exception of a few marking areas, there are no intermediate solutions making it possible to have fairly large opaque areas and transparent complementary areas or vice versa. The teaching of this prior art also does not make it possible to create shades of color on the surface of the dial.

SUMMARY OF THE INVENTION

The present invention therefore aims to overcome the drawbacks of the aforementioned prior art by providing a part in which the combination of two materials having, to the best knowledge of the applicant, never been used together to produce a technical result or a decorative effect by being able to create in said piece transparent, opaque or translucent, colored or not.

[0005] To this end, the subject of the invention is a part for technical and/or decorative use comprising a transparent substrate whose softening point is higher than the temperature necessary to deposit enamel and comprising opaque deposits, translucent or transparent colored or not, said deposits being constituted by layers of enamel.

[0006] The transparent material resistant to a temperature above 500° C. can be a mono or polycrystalline material, for example a quartz, a spinel or a corundum, in particular sapphire. It is also possible to use an amorphous material, such as a mineral glass insofar as its softening point is higher than the temperature necessary to carry out the deposition of enamel.

[0007] According to one embodiment, the enamel deposits are made in recesses machined in at least one face of the substrate, the parts having no recesses can also be covered with layers of enamel, or on the contrary left bare, and therefore be transparent.

[0008] According to another embodiment, the enamel deposits are made in a groove machined in the thickness of the transparent substrate.

[0009] The enamel layers can be thick and or, on the contrary, thin or ultra-thin and translucent, even transparent, or else opaque depending on the pigments entering into the composition of the enamel.

[0010] According to yet other characteristics of the invention, enamel layers of different colors can be provided in different portions of the groove, or even in at least one face of the transparent substrate. When the layers are translucent and have overlapping areas, this allows for additional color or tint.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention will appear in the following description of several embodiments, given by way of illustration and not limitation, with reference to the appended drawings in which: FIG. 1 shows a top view of a wristwatch incorporating a decorative and technical part according to the invention; FIGS. 2 to 5 represent according to section IV-IV of FIG. 1 the different steps of a first embodiment; Figure 6 shows a second embodiment in section; Figure 7 shows a third embodiment in section; FIG. 8 represents a fourth embodiment in section, and FIG. 9 represents in section a fifth embodiment

DETAILED DESCRIPTION OF THE INVENTION

Referring first to Figures 1 to 5 is described below a first embodiment of a part according to the invention used to form the dial 1 of a wristwatch with analog display by means of hour 2a, minute 2b and second 2c hands moving opposite hour markers 4 inscribed on an hour circle 5. In the example shown, dial 1 comprises an aperture 6 crossing the entire thickness of dial 1 and below which moves a date disc 7.

The dial 1 is shown in section in Figure 4 along the line 6 o'clock - 12 o'clock, the scale according to the thickness being greatly exaggerated for a better understanding of the drawings. The dial is formed by a transparent substrate 10 having an upper face 11 facing an observer, the lower face being designated by the reference 12.

The transparent substrate 10 shown in Figure 2 is cut to the dimensions of the dial in a plate having a thickness between 0.4 and 0.9 mm, the material constituting said plate must be able to withstand temperatures above 500 ° C, preferably at temperatures between 700°C and 1300°C. The substrate 10 is pierced in its center with a hole 3 for the passage of the barrels of the needles 2a, 2b, 2c, by known means, for example with a grinding wheel or by ultrasound with a sonotrode. Equivalently, the hole can be executed in a final step in the manufacture of the dial.

As shown in Figure 3, is machined in the upper face 11 of the transparent substrate 10 a recess 13 corresponding to the disc located inside the hour circle 5, said recess having for example a depth of 0.2 mm. In the case of a transparent sapphire substrate 10, the recess 13 is produced by mechanical abrasion (countering, etching) with diamond tools. Depending on the nature of the transparent substrate 10, other machining methods are possible. For example, with a quartz substrate, it is possible, for example, to carry out photochemical machining.

As seen in Figure 4, the hour circle 5 and the recess 13 are covered with enamel layers 23. These enamel layers 23 are obtained by known techniques comprising several steps consisting of a dipping, spraying, dabbing or screen-printing to apply a given enamel composition, and in an oven pass after each step until the desired thickness is obtained. The firing temperature is between 700°C and 1300°C depending on the nature of the enamel composition. To avoid a depression of the enamel layers at the level of the axis hole 3, it is possible to provide a temporary insert (not shown) resistant to heat, for example a ceramic insert, said insert then being eliminated in the finishing step. The finishing stage consists of polishing the two faces with a grinding wheel or fine-grained abrasive paper (9 to 15 µm) to achieve the desired dimensions, then carrying out a final passage in the oven to obtain a glaze of the enamelled surface.

As can be seen, the enamel layers 27 located in the center of the dial are thick, for example 0.4 mm, and may be opaque to light depending on the pigments used in the composition of the enamel. The color visible to the observer will therefore be that of the enamel. On the contrary, the layers of enamel 25 on the chapter ring are thin, and thin enough, for example 0.2 mm, to make them translucent and allow the underlying substrate to be seen. If desired, the underlying substrate may comprise marks or decorations, such as hour markers 4, formed for example by metallization, prior to the steps of forming the enamel layers. The thin and translucent enamel layer 25 therefore makes it possible to read the indications carried by the chapter ring on a background corresponding to the shade chosen for the enamel. It is of course possible, as has been known for a long time, to add marks or decorations to the surface of the enamel, or even to combine the two possibilities to increase the aesthetic choices.

[0018] It will also be observed that the same part manufactured as indicated above can present two different aspects for the observer depending on how the dial 1 is mounted in the case. If the enamel face 11 is oriented on the observer side, the appearance of the opaque zone 27 and of the translucent zone 25 will be shiny. If, on the contrary, the non-enamelled face 12 is oriented on the observer side, the interface between the transparent substrate 10 and the enamel layers 25, 27 will give a slightly grainy appearance. Thus the invention makes it possible, with the same dial production line, to produce two different collections of wristwatches.

[0019] Once the dial is finished, or before the last passage in the oven for glazing, it is possible, as shown in Figure 5, to cut out a large through passage forming the window 6 allowing the information carried by the date disc to be seen. 7, or by any other medium.

Referring now to Figure 6, there is shown in section a second embodiment which differs from the previous embodiment in that the transparent monocrystalline substrate 10 is machined on the face 12 opposite the face directly visible by an observer. Zones 14 are recessed machined and lined with layers of enamel to form a thick opaque layer 24 that does not project beyond the recessed machined parts, thus leaving zones 20 devoid of any enamel coating and therefore totally transparent. The outline of these transparent areas 20 can be provided to allow part of the mechanism to be seen, such as a tourbillon represented schematically by the reference 8.

In Figure 7 there is shown a third embodiment which is in some way a synthesis of the embodiments described above and which includes rear lighting symbolized by an electroluminescent sheet 9. The upper face 11 facing an observer is hollow machined to allow the deposition of thin enamel layers 25 and the deposition of ultra-thin enamel layers 29, for example 0.1 mm. Certain areas of the upper surface 11 are free of enamel deposits and it is assumed that the enamel used has a first color, for example yellow (Y). The lower face 12 is also hollow machined to allow deposits of thin 26 and ultrathin 30 enamel layers, the enamel used having a second color, for example blue (8). In the part situated to the left of the needle hole 3, the upper 25 and lower 26 enamel zones are juxtaposed and the colors visible to an observer will be yellow (Y) and blue (B). The part located to the right of the needle hole 3 comprises an entirely transparent zone, a zone where the upper 29 and lower 30 ultrathin deposits are superimposed to give the green color (G) by mixing the two primary colors, and a zone of the upper surface where the ultra-thin enamel deposit 29 is contiguous with the thin enamel deposit 25.

[0022] For a better understanding of the drawings, the thin and ultrathin enamel deposits have been represented with constant thicknesses, that is to say with recesses having a bottom parallel to the surfaces of the transparent substrate 10. It is well obvious that there is no technical difficulty in making the bottoms of the recesses with an inclined surface gradually varying the thickness of the enamel layers. This variant embodiment, not shown, makes it possible to have shades of the same color or a gradient between two different colors when enamel deposits are made on both sides of the transparent substrate and have overlapping zones. Similarly, and in particular when a face has separate recesses, it is possible to have more than one color of enamel on the same face, or even to create a cloisonné enamel. Figure 8 illustrates a fourth embodiment which can also be combined with the previous embodiments. In this embodiment one of the surfaces, the upper surface 11, has a structuring 21 carried out by laser to draw a hologram then it is coated with thin layers of enamel, said hologram being able to be observed by reflection or by transmission if a rear light 9.

According to the embodiment shown in Figure 9, which corresponds more particularly to the subject of the present invention, the enamel deposit 25 is carried out in a groove 15 machined in the thickness of the transparent substrate 10, according to the techniques mentioned above. This embodiment has the advantage of making the porosities in the enamel mass invisible, of facilitating the machining and polishing operations, including at the level of the opening of the groove 15.

This embodiment can advantageously be combined with the previously described embodiments. The enamel deposited in the groove can, for example, have a first shade and correspond to the hour circle and recesses, formed on the rear face of the dial at the 3 o'clock, 6 o'clock, 9 o'clock, 12 o'clock positions, be lined with an enamel of a second shade to better bring out these hourly positions.

[0025] The dial of a wristwatch has been given purely by way of example, the use of a part made according to the invention not being limited to the watchmaking field. Such a part can be incorporated into any type of case for which it is desirable to have an at least partially transparent panel. It can for example constitute the glass for closing the lid of a jewelry box.

Claims (7)

1. Part for technical and/or decorative use comprising a transparent substrate (10) made of transparent material resistant to a temperature, greater than 500° C., necessary to carry out an enamel deposit, this transparent material being able to be a mono- or polycrystalline, for example a quartz, a spinel or a corundum, in particular sapphire, or even an amorphous material, such as a mineral glass, insofar as its softening point is higher than the temperature necessary to carry out the deposition of enamel, characterized in that the edge of said substrate (10) has a groove (15) machined in its thickness and lined with an enamel deposit (25) opaque, translucent or transparent, colored or not. 2. Part according to claim 1, characterized in that the transparent material forming the substrate (10) is a mono or polycrystalline material, for example a quartz, a spinel or a corundum. 3. Part according to claim 2, characterized in that the transparent material forming the substrate (10) is a sapphire. 4. Part according to claim 1, characterized in that the transparent material forming the substrate (10) is an amorphous material, such as mineral glass. 5. Part according to claim 1, characterized in that the substrate (10) further comprises in at least one of its faces (11, 12) recesses (13,14) also lined with enamel deposits (23 to 30 ). 6. Part according to claim 55, characterized in that the enamel deposits in the groove (15) and the enamel deposits in the recesses (13, 14) have overlapping zones, said deposits possibly having different colors . 7. Part according to any one of the preceding claims, characterized in that it constitutes the dial of a timepiece.