EP3037900B1 - Method for manufacturing a display module for a timepiece comprising a digital device for displaying information - Google Patents

Description

Technical field of the invention

The present invention relates to a method of manufacturing a timepiece comprising a digital information display device. More specifically, the invention relates to such a method for obtaining a timepiece in which the digital display of information is more aesthetic and easier to read.

Technological background of the invention

Wristwatches equipped with a digital information display device such as a liquid crystal cell have been known for a long time. Such wristwatches typically include a dial under and away from which is arranged for example a liquid crystal cell. A window in the dial of the watch allows the user to read hourly or other information displayed by the liquid crystal cell. The liquid crystal cell is fixed on a platen housed in the watch case remote from the dial. There is therefore an unsightly gap between the surface of the dial and the display surface of the liquid crystal cell. In addition, depending on the angle at which the user looks at his watch, his vision may be impeded by the shadow projected by the edges of the window on the display surface of the liquid crystal cell.

Furthermore, the liquid crystal cells that equip the wristwatches of the type described above most often comprise glass substrates joined together by means of a sealing frame. These glass substrates are usually of square or rectangular shape because, even if it is technically possible to give such glass substrates shapes that deviate from the square or rectangular shape, this is hardly possible from a point of view. economic view.

The document DE 198 57 997 discloses a dial under the surface of which are simultaneously attached a liquid crystal cell and a solar cell.

The document US 4,218,872 A discloses a display device for a timepiece comprising a perforated dial and an electro-optical display element attached to the dial so that the display element can be seen through the opening. The display device also includes an insulating layer and electrodes on the insulating layer.

Summary of the invention

The present invention aims to overcome the problems mentioned above as well as others by providing a method for simplifying the manufacture of a timepiece comprising a dial under which is disposed a digital display device. information.

The present invention relates to a method of manufacturing a timepiece comprising a dial under which is disposed a digital information display device, a window formed in the dial of the watch allowing a user to read the information displayed by the digital information display device, the dial having an upper face and a lower face and the digital information display device having a top information display surface, the method being characterized in that the the top surface of the display is provided with information of an adhesive layer and in that the digital display device is rolled up information on the underside of the dial through the adhesive layer.

According to a complementary characteristic of the invention, after fixing the digital information display device on the dial, the assembly is passed through an autoclave in order to expel the air possibly trapped between the adhesive layer and the dial. Preferably, the pressure in the autoclave is 6 bar, the treatment temperature is of the order of 50 ° C and the treatment time is about 30 min.

Brief description of the figures

• la figure 1 est une vue en perspective et en éclaté d'un premier mode de réalisation d'une pièce d'horlogerie obtenue grâce au procédé selon l'invention ;
• la figure 2 est une vue en perspective et en éclaté d'un second mode de réalisation d'une pièce d'horlogerie obtenue grâce au procédé selon l'invention, et
• les figures 3A et 3B sont respectivement des vues d'ensemble et de détail à plus grande échelle d'un cadran en plastique auquel est conféré un aspect de matériau composite du type fibre de carbone.

Other features and advantages of the present invention will emerge more clearly from the detailed description which follows of an exemplary embodiment of the timepiece according to the invention, this example being given for purely illustrative and nonlimiting purposes only in connection with the attached drawing in which:

• the figure 1 is a perspective and exploded view of a first embodiment of a timepiece obtained by the method according to the invention;
• the figure 2 is a perspective and exploded view of a second embodiment of a timepiece obtained by the method according to the invention, and
• the Figures 3A and 3B are respectively larger scale and overall views of a plastic dial which is imparted an aspect of composite material of the carbon fiber type.

Detailed description of an embodiment of the invention

The present invention proceeds from the general inventive idea which consists, in the case of a timepiece comprising a dial on the lower side of which is fixed a digital information display device, to provide a manufacturing method for simplifying the production of such a display module.

The figure 1 is a perspective view and exploded of a first embodiment of a display module for a timepiece obtained by the method according to the invention. Designated as a whole by the general numerical reference 1, this display module comprises a dial 2 which, in the example shown, is of generally circular shape. However, it will be understood that the shape of the dial may deviate from a circular profile and may be for example square or rectangular. The dial 2 has an upper face 4 and a lower face 6 and is pierced with a hole 8 at its center for the passage of a set of axes of the minute and second hands (not shown in the drawing). A window 10 is provided in the dial 2. In the case where the dial 2 is made of a transparent material, the decorative layer whose dial 2 is coated is omitted at the location corresponding to the window 10. Another solution to form the window 10 is to pierce the dial 2 at the desired location.

The display module 1 also comprises a digital information display device. In the example shown in the drawing, this digital information display device consists of a flexible liquid crystal display cell 12 which has a substantially semicircular shape. This liquid crystal display cell 12 comprises a front substrate 14 which defines an upper display surface and a rear substrate 16. The front 14 and rear 16 substrates are made of a flexible plastic material and are conventionally connected between them by a sealing frame (not visible in the drawing) which delimits a closed volume for the confinement of the liquid crystal. It goes without saying that this example is given purely for illustrative purposes only and that the digital information display device may be of the electrophoretic type or may also use an electronic ink. A flexible electrical connector 18 makes it possible to connect the electrodes of the cell liquid crystal display 12 to an electronic control circuit (not shown).

According to the invention, the front substrate 14 of the liquid crystal display cell 12 is coated with an adhesive layer 20 formed of an optically transparent adhesive and through which the liquid crystal display cell 12 is applied against the lower face 6 of the dial 2. The liquid crystal display cell 12 is mechanically laminated against the lower face 6 of the dial 2, then the assembly formed by the dial 2 and the crystal display cell liquid 12 is passed through an autoclave in order to expel the air possibly trapped between the adhesive layer 20 and the dial 2. By way of example, the pressure in the autoclave is 6 bars, the treatment temperature is order of 50 ° C and the treatment time is about 30 min.

The assembly is completed by a first solar cell 22. It will be understood that the use of this solar cell 22 corresponds to the preferred embodiment of the invention but that, in the basic variant of the invention, the display module 1 includes only the dial 2 and the liquid crystal display cell 12. In the example shown in FIG. figure 1 the solar cell 22 has a substantially semicircular shape complementary to the shape of the liquid crystal display cell 12. The sum of the area of the liquid crystal display cell 12 and the solar cell 22 corresponds to substantially to that of the dial 2.

The solar cell 22 is arranged under and at a short distance from the dial 2. For this purpose, it is received in a plate 24 which is adapted in shape and dimensions to those of the dial 2. For the axial retention of the solar cell 22, the plate 24 comprises a bearing surface 26 whose area is substantially equal to that of the solar cell 22. For its radial maintenance, the solar cell 22 is provided along its outer perimeter of at least one and, preferably , two pins 28 which are engaged in two corresponding housing 30 provided on the periphery of the plate 24. As can be seen in the drawing, the bearing surface 26 is pierced by two diametrically opposite through holes 32 in which are engaged springs 34 which ensure electrical contact between the two terminals of the solar cell 22 and the power supply circuit of the watch (not shown).

The assembly formed by the dial 2 and the liquid crystal display cell 12 is disposed above the solar cell 22 and bears on a peripheral rim 36 of the plate 24. It can be seen that the display cell liquid crystal 12 is located above an opening 38 formed in the plate 24 and whose extent substantially corresponds to the surface of the liquid crystal display cell 12. This opening 38 allows a backlight device 40 mounted from below the plate 24 to illuminate the liquid crystal display cell 12 from the rear.

Finally, the assembly formed by the dial 2, the liquid crystal display cell 12 and the solar cell 22 is detachably immobilized on the plate 24 by means of flexible locking hooks 42. A module of FIG. 1 complete display that can be exchanged piece for room in case of malfunction. In case of problems, it is even possible to remove the display module 1 and replace only the (or) component (s) defective, which is very advantageous from an economic point of view.

The figure 2 is a perspective and exploded view of a second exemplary embodiment of a display module for a timepiece obtained by the method according to the invention. In all that follows, elements identical or similar to those already described in connection with the figure 1 will be designated by the same numerical references.

We see on the figure 2 that the dial 2 comprises a window 10 adapted in shape and dimensions to the shape and dimensions of the front substrate 14 which defines the upper display surface of the liquid crystal display cell 12. It is also seen that a second solar cell 220 has substantially the same dimensions as the dial 2 and is provided with an opening 221 in which is housed the cell liquid crystal display 12 when the solar cell 220 is disposed under the dial 2. It is understood that when there is under the dial 2 a solar cell of the same dimensions as the dial 2, a part of the surface of the solar cell will be masked by the liquid crystal display cell 12. However, it has been found that the photovoltaic conversion efficiency of a given active surface solar cell is less good when the solar cell is partially obscured than when the active surface of the solar cell is reduced due to the presence of a shape opening in which the digital information display device is housed.

For the rest, the display module illustrated in the figure 2 is identical to that described above in connection with the figure 1 . The liquid crystal display cell 12 is fixed on the lower face 6 of the dial 2 by rolling and the solar cell 220 is received in the plate 24. Thereafter, the assembly formed by the dial 2 and the cell of FIG. The liquid crystal display 12 is disposed over the solar cell 220, so that the solar cell 220 is under and at a small distance from the dial 2 and the liquid crystal display cell 12 is housed in the opening 221. A backlight device 40 mounted below the plate 24 makes it possible to illuminate the liquid crystal display cell 12 from the rear through the opening 38 formed in the plate 24. The assembly formed by the dial 2, the liquid crystal display cell 12 and the solar cell 220 are removably attached to the plate 24 by means of a plurality of flexible locking hooks 42.

As can be seen in the drawing, the bearing surface 26 is pierced with two through-holes 32 placed close to one another on a diameter portion of the bearing surface 26 in which springs 34 are engaged. which make it possible to ensure the electrical contact between the two terminals of the solar cell 220 and the electric supply circuit of the watch (not shown). We also see that, for its radial maintenance, the solar cell 220 is provided on its device with at least one and, preferably, three notches 44 which cooperate with three corresponding pins 46 of the plate 24.

In the case where the timepiece is of the solar watch type, the dial 2 must be at least partially transparent in order to let a sufficient amount of light to allow the solar cell 22, 220 to effectively recharge the battery of the shows while masking the solar cell 22, 220 with regard to the wearer.

For example, the dial 2 can be made of a transparent plastic material and be covered with a layer of paint whose opacity is adjusted according to the thickness of the paint layer and / or the concentration of the pigments in the paint. The transmittance of a dial 2 of transparent plastic covered with paint is of the order of 45%. In other words, 45% of the incident light is transmitted to the solar cell 22, 220 and the rest of the light is absorbed by the dial 2, which is sufficient to mask the solar cell 22, 220 with respect to the user. In another example, the plastic dial 2 may be covered with a layer of mother-of-pearl whose thickness is typically 150 μm ± 20 μm and whose transmittance is adjusted to 35%. The mother-of-pearl layer is fixed on the upper surface 4 of the dial 2 by means of an optically transparent layer of adhesive.

According to yet another aspect, it is sought to give the plastic dial 2 a carbon fiber composite material appearance. It is known that such a composite material is obtained by means of interleaved carbon fibers which are impregnated with resin, the surface state of the resulting material having slightly raised areas which are repeated periodically.

To imitate such a texture, two solutions are envisaged. The first solution consists in machining in the inner wall of the mold into which the plastics material is injected structures which will form as many zones in relief on the surface of the dial 2. The second solution uses the principle of a conventional pad printing (decal with cliché) or an electronic printing that is also possible from a technical point of view but whose rendering for the eye is however a little less good. As illustrated on Figures 3A and 3B attached to this patent application, the carbon effect is obtained by the alternating and periodic repetition of horizontal lines 48 and vertical lines 50. Even if the horizontal lines 48 seem brighter, this is only due to the angle of incidence of light. This effect makes the dial "live" depending on the light and it's exactly the same with real carbon. The lines are black (horizontal lines and vertical lines). We could also use a mixture of black (vertical lines) and gray (horizontal lines) to obtain the carbon effect, but in this case it would be independent of light and quite static.

Note that in the embodiment illustrated in FIG. figure 1 the liquid crystal display cell 12 and the first solar cell 22 each have a clearance, respectively 52 and 54, for the passage of the hour and minute pin axes. Similarly, a through hole 56 is formed on the edge of the bearing surface 26 of the plate 24 and the backlight device 40 is pierced with a hole 58. Similarly, the second solar cell 220 is pierced with a hole 60 at its center and the plate 24 is provided with a hole 62 defined by a guide flange 64.

Claims (3)

1. Method for manufacturing a timepiece including a dial (2) underneath which is disposed a digital information display device, an aperture (10) provided in the watch dial (2) allowing a user to read the information displayed by the digital information display device, the dial (2) having an upper face (4) and a lower face (6) and the digital information display device having an upper information display surface, the method being characterized in that the upper information display surface is provided with an adhesive layer (20) and in that the digital information display device is laminated on the lower face (6) of the dial (2) by means of the adhesive layer (20).
2. Method according to claim 1, characterized in that, once the digital information display device has been secured to the dial (2), the assembly is placed in an autoclave to expel any air trapped between the adhesive layer and the dial.
3. Method according to claim 1, characterized in that the pressure in the autoclave is 6 bars, the treatment temperature is on the order of 50°C and the treatment time is around 30 minutes.

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