HK1119788B - Analog display element made of crystalline material, timepiece provided with a display element of this type and method for the production thereof - Google Patents

Description

Analog display member made of crystalline material, timepiece fitted with such a member and method of manufacturing such a member

Technical Field

The present invention relates to an analog display member such as a timepiece hand.

The invention also relates to a timepiece and a method of manufacturing a display member.

Background

The manufacture of hands for use as display members in timepieces is particularly complex, particularly when the hands are to be fitted to the top of the range of the timepiece, for which purpose the hands must have a particularly polished surface appearance, possibly with facets.

Currently, pointers have been made in brass, steel, gold, aluminum, or special alloys. They may be treated galvanically, covered with paint, oxidized or left untreated if gold is used as the material. They are generally made by machining or molding.

However, satisfactory dimensional accuracy is still not achieved with machining and embossing techniques for these materials, and additional deburring, polishing, etc. operations are required to obtain the final pointer shape.

Furthermore, it is generally necessary to apply various treatments to the pointer to ensure a high quality surface finish.

Further, current hand manufacturing techniques do not allow to obtain all the desired forms, thus constraining the creativity of the timepiece designer.

Disclosure of Invention

The object of the invention is to propose a pointer which is easier to manufacture, while providing a large degree of freedom of design for its form, and which can be manufactured continuously to minimize production costs.

The invention therefore proposes an analogue display member fitted to a timepiece, of the type comprising a main body in which a spindle hole is arranged, the spindle hole being fitted to a driving spindle, characterized in that the main body is made of a silicon-based crystalline material. Preferably, the body of the analogue display member has the shape of a timepiece hand.

The display member according to the invention has the advantage of being able to be manufactured easily using techniques which have been proven in the field of microelectronics for manufacturing integrated circuits and in the field of micromachines for manufacturing microstructures.

Silicon has the advantage of being very light, since its density is approximately 2.49kg/dm³This minimises the mass of the display member and therefore minimises the problems of inertia and imbalance, particularly when the display member is in the form of a pointer. Furthermore, the imbalance and reduction of inertia of the display member is of the size of the display member driving device and of the display member driving deviceThe energy consumption of the drive device of (2) has a positive effect.

According to other features of the invention:

the body comprises a proximal portion in which the mandrel aperture is arranged and a distal portion forming an indicator portion of the pointer, and the distal portion is linked to the proximal portion by at least one beam having a width in a plane transverse to the mandrel of less than or equal to one hundred microns;

the body includes a plurality of apertures parallel to the drive spindle within a thickness thereof, and the apertures are less than fifty microns in diameter;

the top surface of the body includes a raised pattern;

the top surface of the body includes facets;

at least one face of the body is provided with a coating made of a different material from the body;

the coating is made of metal;

the display member includes at least one integrated circuit element disposed within a thickness of the body;

the crystalline material is monocrystalline silicon.

The invention also proposes a timepiece characterized in that it comprises at least one analog display member according to one of the preceding features.

The invention further proposes a method of manufacturing analogue display members to be fitted to a timepiece, each analogue display member comprising a body in which a spindle hole is arranged, the spindle hole being fitted to a driving spindle, characterized in that the method comprises at least one step of micro-machining a plate of silicon-based crystalline material to make at least one body with its spindle hole in said crystalline material.

The method is easy to implement for mass production of precise light parts.

According to other features of the method according to the invention:

during the plate micromachining step, a flexible element is formed on the main body to allow the analog display member to be mounted on the driving spindle by elastic deformation of the flexible element;

performing a micro-machining step to simultaneously form a plurality of analog display members in the same plate;

the micro-machining step comprises at least one lithography step to reproduce on the plate the outline of at least one portion of the body of an analog display member;

the method comprises at least one step of depositing a coating on at least one face of the body of each analogue display member;

the method includes at least one step of micro-machining a top surface of the body to form a raised pattern on the top surface;

the method includes at least one step of micro-machining a top surface of the body to form facets on the top surface;

the crystalline material is monocrystalline silicon.

Drawings

Other characteristics and advantages of the invention will become clearer from the following detailed description, given by way of non-limiting example, with reference to the attached drawings, in which:

figures 1 to 6 are vertical sections schematically illustrating several steps of a method for manufacturing a timepiece hand from a silicon plate according to the teachings of the present invention;

FIGS. 7a and 7b are top views schematically showing the silicon plate in the step illustrated in FIG. 6;

figure 8 is a top view schematically showing a watch equipped with at least one hand obtained by the method according to the invention;

fig. 9 is a vertical section schematically illustrating a pointer obtained by the method according to the invention;

fig. 10 is a top view schematically illustrating a pointer provided with two longitudinal facets obtained by the method according to the invention;

FIG. 11 is a vertical section taken along section plane 11-11 of the pointer of FIG. 10;

fig. 12 is a top view schematically illustrating a pointer provided with two connection beams obtained by the method according to the invention;

FIG. 13 is an enlarged view of a portion of the beam of FIG. 12;

FIG. 14 is an axial cross-section taken along plane 14-14 showing in enlarged form the distal portion of the pointer of FIG. 12;

Detailed Description

Figures 1-7 illustrate several steps of a method for manufacturing an analog display member 10 according to the teachings of the present invention.

The analog display means 10 is here a pointer 10, an example of which is schematically shown in fig. 9.

According to the teachings of the present invention, each hand 10 comprises a body 11 made of a silicon-based crystalline material.

Here, the "silicon-based crystalline material" means a crystalline material containing silicon, such as single crystal silicon, polycrystalline silicon, and quartz.

Preferably, pointer 10 according to the present invention is micromachined in a monocrystalline silicon plate 12, monocrystalline silicon plate 12 being similar to the silicon plates used to make integrated electronic circuits, such plates being commonly referred to as "wafers".

Advantageously, a series of several hands 10 are made in the same silicon wafer 12 according to a method called "batch" using techniques derived from the microelectronics field, which make it possible to manufacture mechanical microstructures in the silicon wafer 12.

These techniques have been implemented for the fabrication of pressure sensors, accelerometers, micro-actuators and micro-pumps. They mainly include two types of manufacturing methods, i.e., dry etching and wet etching.

These methods generally use masking techniques that locally remove a layer of material of a determined thickness.

The dry etching method uses, for example, a laser beam or a high-density plasma source.

According to a preferred embodiment of the invention, the technique used for micro-machining the silicon wafer 12 is used to make the pointer 10 directly within the thickness of the silicon wafer.

Electropolishing is an example of a technique for silicon etching. This technique, which uses the property of single crystal silicon to be porous by anodic electrochemical etching in hydrofluoric acid using a low current density, can completely remove silicon at a high current density.

An exemplary implementation of the silicon electropolishing technique is set forth in the publication entitled: "electrochemical contamination of Multi-walled Microchannels" by R.W. Tjerkstra et al, "Proceedings of Micro Total Analysis Systems 98 Workshop", page 133-136, Banff, Canada, in the context of the manufacture of coaxial microchannels whose partition walls are made of porous silicon. Reference is made to this publication, which is hereby incorporated by reference for further details of the process.

Other examples of silicon micromachining processes are described in the following works: entitled "Fundamentals of Micropathology" edited by Marc Madou, by CRC Press, and by ISBN 0-8493-9451-1, which is hereby incorporated by reference for further details.

The main steps of the method according to the invention will be described in a simplified manner.

Fig. 1 shows a silicon wafer 12 before the method according to the invention is carried out.

Fig. 2 illustrates the step of depositing a sacrificial layer 14 on the top surface of the silicon wafer 12.

Figure 3 illustrates the processing of the sacrificial layer 14 through the mask 16 to locally alter the structure of the sacrificial layer 14 to draw a pattern representing a series of fingers 10 on the silicon wafer 12.

In fig. 5, the silicon wafer 12 has been etched through a sacrificial layer, preferably according to an anisotropic etching technique, so that the pattern representing the pointer 10 is now drawn within the thickness of the silicon wafer 12.

The remaining sacrificial layer 14 is then removed, as shown in fig. 6.

A silicon wafer 12 is thus obtained in which the hands 10 are pre-cut and remain attached to the body of the wafer 12 by means of material bridges, as shown in fig. 7a and 7 b.

The final manufacturing step of the pointer 10 involves separating the pointer from the silicon wafer 12.

Advantageously, the method according to the invention comprises at least one step during which a coating, for example a metal, is deposited on the needle 10 formed of silicon. The coating may be deposited according to chemical vapor deposition or physical vapor deposition techniques.

The method according to the invention also comprises a chemical and/or thermal treatment applied to the surface of the pointer 10 formed of silicon, for example to modify the appearance of the silicon surface.

It should be noted that the etching step may also be carried out to change the appearance of the silicon surface by forming geometric or other patterns, or to change the surface appearance of a coating deposited on the silicon, which provides a meaningful optical effect. Such a geometric pattern may, for example, give the surface of the pointer 10 made in silicon a needle-etched type appearance. Such an etching step may be carried out while the pointer 10 is still carried by the silicon wafer 12.

According to the embodiment shown in fig. 9, the top surface of the pointer 10 is provided with a geometrical pattern 24 of bumps, which is made by silicon etching. A metal deposit 26 is formed on these geometric patterns 24, which gives the pointer 10 the appearance of a needle-etched metal. It should be noted that for a pointer 10 whose body 11 is made of metal, this result would be very difficult to obtain.

According to the embodiment shown in fig. 10 and 11, two longitudinal facets 28 are etched in the top surface of the pointer 10.

Depending on the embodiment, the pattern 24 and facets 28 may have a curved profile to form a wave within the surface of the pointer 10.

It should be noted that the method of manufacturing the pointer 10 according to the invention easily allows to make the pointer 10 with a very variable external appearance.

Advantageously, the method according to the invention can be carried out in parallel on several silicon wafers 12, so as to simultaneously make pointers 10 with similar characteristics within the several silicon wafers 12.

Fig. 8 shows a watch 20 provided with at least one silicon hand 10 made according to the method of the invention.

Each hand 10 is intended to be rotatably connected to a stem or wheel of a watch core (not shown) of the watch 20. Here, the pointer 10 is thus provided with a spindle bore 32 to advance onto a drive spindle 34.

Advantageously, the inner axial surface of the mandrel bore 32 is provided with a layer of material 36, the layer of material 36 enabling the pointer 10 to be advanced by deforming the layer 36 or by sliding against the layer 36, thereby limiting the risk of breaking the body 11.

According to an alternative embodiment, the pointer 10 according to the invention may be bonded or welded to the driving arbour 34.

According to an advantageous embodiment of the invention, shown in fig. 9, the integrated circuit element 22 is made within the thickness of the silicon wafer 12 within the body 11 of the pointer 10.

The integrated circuit element 22 may be fabricated in accordance with conventional microelectronic fabrication techniques before, during, or after the fabrication method according to the present invention is implemented. Thus, the integrated circuit element 22 can be prefabricated in the silicon wafer 12 from which the pointer 10 is manufactured, as shown in fig. 1.

The integrated circuit element 22 may be electrically connected to the control circuit of the watch 20 by means of the rotary arbour of the hands 10.

The integrated circuit element 22 comprises, for example, an integrated light emitting diode within the thickness of the pointer 10. The pointer 10 can thus be lit from the inside by exploiting the transparent properties of silicon.

The integrated circuit element 22 may include a sensor provided to provide an indication to the control circuitry of the watch 20 as to the angular position of the hands relative to the dial.

Fig. 12 to 14 show a modified embodiment in which the pointer 10 is made entirely of silicon, i.e. its body 11, which forms the mechanical structure of the pointer 10, is made of silicon and defines the external shape of the pointer 10. Of course, the body 11 may be coated with one or more coatings, such as a metallic coating.

According to the embodiment shown, the body 11 comprises a ring-shaped proximal portion 38 in which the spindle hole 32 is arranged to mount the hand 10 on the driving spindle 34 of the watch 20. A spindle bore 32 is provided to fit over a drive spindle 34 so that the pointer 10 is secured to the drive spindle 34 in a manner similar to advancement.

The spindle bore 32 is here provided with a flexible element 40 having a tongue-shaped form, the flexible element 40 being made in one piece with the proximal portion 38 of the body 11 and protruding onto the inner surface of the spindle bore 32. The flexible element 40 is provided to deform elastically when the pointer 10 is mounted on the drive spindle 34. Thus, after assembly, the flexible element 40 exerts a clamping force on the drive arbour 34, which holds the pointer 10 axially and rotationally connects the two elements on the drive arbour 34.

The flexible element 40 is preferably formed during the step of micro-machining the silicon wafer 12.

The body 11 also includes a distal portion 42 that forms the indicator portion of the pointer 10. The distal portion 42 has here a triangular form, but it may have any other suitable form to indicate a determined angular position on the dial of the timepiece 20.

The distal portion 42 is connected to the proximal portion 38 by two beams 44, 46, the width 11 of the two beams 44, 46 in a plane transverse to the drive spindle 34 being between thirty and two hundred microns, and preferably equal to fifty microns. A width 11 of fifty microns provides a good compromise between stiffness and acuity of the beams 44, 46.

Thus, the hands 10 are obtained, when the user of the watch 20 views the indications given by the hands 10, only the proximal portions 38 and the distal portions 42 of the hands 10 are actually visible, in particular in a top view. Indeed, in combination with a very small thickness, for example between thirty and one hundred microns, preferably equal to fifty microns, the small width 11 makes the beams 44, 46 almost invisible to the naked eye and therefore makes the elements below the hands 10 between the proximal portion 38 and the distal portion 42 more visible, in particular for the elements displayed on the dial of the watch 20. Furthermore, the use of these barely visible beams 44, 46 provides more freedom in the design of pointer 10 by hiding portions of the structure of pointer 10.

Of course, the pointer 10 according to the invention may comprise more than two beams 44, 46. The number of beams 44, 46 may be chosen as a function of the shape of the pointer 10, in particular as a function of the shape of the distal portion 42, to ensure sufficient rigidity and shock resistance for the pointer 10.

Fig. 13 is an enlarged view of the beam 46 of fig. 12, and it can be seen that the beam 46 can be provided with recesses 48 arranged in a suitable manner to lighten the structure of the pointer 10 without significantly deteriorating its rigidity and shock resistance. The recesses 48 are here formed by slits or windows aligned and distributed over the length of the beam 46, defining a bridge of material between two parallel portions forming the beam 46.

Advantageously, as can be seen in fig. 14, the body 11 of the pointer 10 comprises, within its axial thickness, a plurality of generally cylindrical apertures 50, the apertures 50 being substantially parallel to the drive spindle 34 and having a diameter of less than fifty microns, preferably between three and ten microns. The purpose of these apertures 50 is to reduce the imbalance and inertia of the pointer 10. Since the mass of the beam has very little effect on the imbalance and inertia of the pointer 10, the apertures 50 are preferably arranged only in the distal portion 42, but they may also be arranged in other portions of the body 11.

Here, the orifice 50 passes through the entire thickness of the body 11. They are of sufficiently small size to be invisible to the naked eye of a user of watch 20 so that they do not adversely affect the aesthetic appearance of hand 10.

Claims (20)

1. An analog display member (10) to be fitted to a timepiece (20) of the type including a main body (11), a spindle hole (32) being made in the main body (11), the spindle hole (32) being fitted to a driving spindle (34), characterized in that: the body (11) is made of a silicon-based crystalline material and the analogue display means (10) comprise at least one integrated circuit element (22) arranged within the thickness of the body (11).

2. The analog display member (10) of claim 1, characterized in that: the integrated circuit element (22) comprises an integrated light emitting diode within the thickness of the body (11).

3. The analog display member (10) of claim 1, characterized in that: the integrated circuit element (22) comprises a sensor indicating the angular position of the body (11) with respect to the dial.

4. The analog display member (10) of claim 1, characterized in that: the main body (11) has the shape of a timepiece hand.

5. The analog display member (10) of claim 1, characterized in that: the body (11) includes a plurality of apertures (50) within its thickness parallel to the drive spindle (34), and the apertures (50) are less than fifty microns in diameter.

6. The analog display member (10) of claim 1, characterized in that: the main body (11) includes a flexible element (40) made in a single piece with the main body (11), and the flexible element (40) extends into the spindle hole (32) to allow the analog display member (10) to be fitted on the driving spindle (34) by elastic deformation of the flexible element (40).

7. The analog display member (10) of claim 1, characterized in that: the top surface of the body (11) includes a raised pattern (24).

8. The analog display member (10) of claim 1, characterized in that: the top surface of the body (11) includes facets (28).

9. The analog display member (10) of claim 1, characterized in that: at least one face of the body (11) is provided with a coating (26) made of a different material from the body (11).

10. The analog display member (10) of claim 9, characterized in that: the coating (26) is made of metal.

11. The analog display member (10) of claim 1, characterized in that: the crystalline material is monocrystalline silicon.

12. Timepiece (20), characterized in that: comprising at least one analog display member (10) according to claim 1.

13. A method of manufacturing analog display members (10) to be fitted to a timepiece (20), each analog display member (10) including a main body (11), a spindle hole (32) being arranged in the main body (11), the spindle hole (32) being fitted to a driving spindle (34), characterized in that: the method comprises at least one step of micro-machining a wafer (12) of silicon-based crystalline material to produce at least one body (11) with said mandrel hole (32) in said crystalline material; and a step of arranging at least one integrated circuit element (22) within the thickness of the body (11).

14. The manufacturing method according to claim 13, characterized in that: during the micro-machining step of the wafer (12), a flexible element (40) is formed on the body (11) to allow the assembly of the analogue display member (10) on the drive spindle (34) by elastic deformation of the flexible element (40).

15. The manufacturing method according to claim 13, characterized in that: a micromachining step is performed to simultaneously fabricate several analog display components (10) within the same wafer (12).

16. The manufacturing method according to claim 13, characterized in that: the micro-machining step comprises at least one lithography step to reproduce on said wafer (12) the profile of at least one portion of the body (11) of an analog display member (10).

17. The manufacturing method according to claim 13, characterized in that: the method comprises at least one step of depositing a coating (26) on at least one face of the body (11) of each analogue display member (10).

18. The manufacturing method according to claim 13, characterized in that: the method includes at least one step of micro-machining the top surface of the body (11) to form a raised pattern (24) in the top surface.

19. The manufacturing method according to claim 13, characterized in that: the method includes at least one step of micro-machining the top surface of the body (11) to form facets (28) in the top surface.

20. The manufacturing method according to claim 13, characterized in that: the crystalline material is monocrystalline silicon.