HK1073506B - Ceramic element for watch case and method of manufacturing the same - Google Patents

Description

The present invention relates to a process for manufacturing a ceramic element intended to be reported on a watch case, the visible surface of which bears patterns, and a ceramic element obtained by this process.

A method for depositing a metallic layer on a ceramic substrate consisting of depositing a first layer of CuO or Ti of at least 100 nm followed by a second layer of copper, silver, gold or nickel has already been proposed in DE 2'533'524 and EP 0'230'853. The adhesion between the two layers is obtained by passage through the kiln. In the case of copper and CuO, the temperature of the kiln must be between the eutectic point of CuO and the melting point of copper between 1068° and 1078°C, a temperature which is totally incompatible with the use of a photoforming resin, so that such processes do not allow the masts to be kept for subsequent electroplating.

Since these processes do not allow the use of photosensitive materials, according to techniques commonly used for the manufacture of electronic components in particular, they cannot therefore be used to selectively grow patterns such as figures by electromoulding, since such masks would not withstand the temperature of the oven coating treatment.

A method for forming signs on watch parts of non-electrically conductive material has also been proposed in CH 636' 238 in which a metallic layer such as Cr is deposited on the watch parts under vacuum, this metallic layer is coated with a photosensitive resin in which openings corresponding to the shape of the signs are formed, and a layer of a second metal such as Au, Ni, Rh, Va is deposited by electrochemical means, which is deposited on the first metallic layer through the openings in the photosensitive resin layer.

The purpose of the present invention is to remedy, at least in part, the aforementioned disadvantages.

To this end, the present invention relates first to a manufacturing process for a ceramic element intended to be mounted on a watch case and whose visible surface has patterns, as claimed 1.

The essential advantage of this invention is that it allows the selective formation of patterns, without any form limitation, giving rise to a new product, offering original aesthetic possibilities, allowing the renewal and improvement of the appearance of watches, in particular that of fixed and rotating-lens watches.

The process according to the present invention allows for excellent adhesion of the embossed patterns to the surface of the ceramic element, which is of great importance, especially when the patterns are embossed, since a wristwatch case in particular is highly exposed to all kinds of external stresses, including shocks.

The advantage is that the visible surface on which the patterns are formed is a trunk- or pyramid-trunk-shaped surface, which therefore requires a special masking technique.

Other features and advantages will be shown in the following description, which will be made by reference to the attached drawings which illustrate, schematically and by way of example, a form of execution and a variant of implementation of the process of the present invention, and the ceramic elements obtained by this process. Figures 1 to 4 illustrate different steps in the process of preparing a ceramic element seen in the cut to be mounted on a watch case, the subject of the present invention;Figures 5 and 6 illustrate a form of execution of pattern formation in relief;Figure 7 illustrates a variant for obtaining patterns on the surface of the ceramic element;Figure 8 is a partial cut view of a ceramic bezel ring according to the present invention.

Figure 1 shows a sintered substrate 1 in ZrO2, Al2O3 or a mixture of the two on the surface of which a layer 2 of a photosensitive polymer is deposited to form a conformal layer for the selective deposition of the patterns.

A mask is applied to this layer 2 of RISTON® MM150 type photosensitive polymer in order to selectively insulate this layer 2 under UV light to polymerize the parts of layer 2 of photosensitive polymer that should remain on the substrate 1. This layer 2 is then developed in a bath of Na2CO3 at 0.85% as directed by the supplier of the photosensitive polymer to dissolve the uninsulated parts of layer 2 to reveal portions of surface 1a of the substrate 1. These portions correspond to the shapes chosen for the formation of the patterns as shown in Figure 2. This is a standard photolithographic process.

It should be noted that in the examples shown, the substrate 1 shown in Figures 1 to 7 in cut form actually corresponds to a portion of the ceramic element of the present invention. This portion may correspond in particular to a radial section of this ceramic element consisting of a circular ring of rectangular cross-section. Preferably, this ring has a trunk shape, so that the visible surface 1a is inclined with respect to the axis of revolution of this ring.

For this reason, the mask used for pattern formation in polymer layer 2 is not a conventional mask, but a polymer mask, thermoformed to give it a complementary shape to that of the ceramic substrate.

Once this pattern formation operation has been completed, substrate 1 is placed, thus selectively coated with layer 2, in a vacuum coating enclosure, in which a first coating layer 3 of Ti, Ta, Cr or Th of at least 100 nm is deposited (Figure 3) by the physical vapor deposition (PVD) technique and magnetron cathodic spraying which allows to ensure a higher adhesion of the coating layer 3 than would be obtained by using the PVD magnetron technique.

While maintaining the vacuum in the storage chamber, a second layer 4 (Figure 4) is formed by magnetron cathodic spraying using a target of type Au, Ag, Pt, Pd, TiN, CrN, Ni ZrN. The thickness of this second layer is at least 100 nm, preferably between 500 nm and 15 μm.

Equipment used for vacuum deposition by cathodic magnetron spraying includes:a cylindrical stainless steel enclosure with a turbomolecular pumping system and a rotary pallet pump;a carousel-type substrate carrier with a vertical axis of rotation and substrates positioned vertically.Ability to perform polarized RF cathodic spraying on the carrier-substrate;two vertical rectangular magnetron cathodes mounted facing the carousel at an angle of 120° to the axis of the carousel;cathodes: a Ti99.99 target, an Au99.99 target, a cathode feed by a 600 W 13.56 MHz RF generator with a manual impedance tuning box, a gas supply (purity: 5.7-6.0) per mass flow meter, a Penning pressure gauge for limit vacuum control and a capacitive gauge (absolute measure) for working pressure control.

The parts were cleaned in an ultrasonic bath in a mixture of 20% isopropyl alcohol and 80% deionized water for five minutes.

The substrate is stripped by vacuuming the enclosure and pumping to a pressure below 5 x 10-2 Pa. Ion cleaning of the substrate surface is performed by reverse spraying: The test chemical is used to determine the concentration of the test chemical in the test medium.

The conditions for depositing the titanium substrate are as follows: RF power on cathode: > 150 W Argon flux: > 5 cm3/min Argon pressure: < 5 Pal Layer thickness is > 100 nm, preferably > 100 nm and < 1500 nm

While maintaining the vacuum in the enclosure, the substrates are moved by rotation of the carousel to a small cathode equipped with the Au99.99 target. RF power on cathode: > 50 W Argon flux: > 10 cm3/min Argon pressure: < 5 Pal Layer thickness is > 100 nm, preferably > 500 nm and < 15 μm

The substrates thus obtained are completely covered with the gold-coated titanium bonding layer, as shown in Figure 4.

After depositing this second layer 4, we take the substrate out of the vacuum deposit enclosure and have a choice between two solutions.

The first embodiment of the invention is to electroform substrate 1 selectively coated with polymer layer 2 and layers 3 and 4 (Figure 4) using the same noble metal as the second layer 4, gold. The advantage of the invention is that it can keep the polymer mask intact for use in the subsequent selective electroplating operation. An additional layer 5 of the desired thickness is then deposited by electroplating. The gold bath used in this case is high in Au and allows an electroplating time of at least 0.10 μm, preferably 10 mm thick.

In a second embodiment, as shown in Figure 7, after the substrate with the selective coating of layers 3 and 4 has been removed, the polymer layer 2 is dissolved as was done previously to pass from the step in Figure 5 to that in Figure 6, so that only layers 3 and 4 remain on substrate 1 which were on parts 1a where the ceramic substrate was not covered by the dissolved polymer layer 2.

Alternatively, instead of being a truncated ring, the ceramic element of the present invention could be a polygonal frame with a face inclined to the central axis of the element and thus form a pyramidal trunk.

Figure 8 shows a ceramic ring 1 of truncated shape, which is intended to be brought back by elastic deformation on a bezel.

Claims (9)

1. A process for manufacturing a ceramic element intended to be fitted onto a watch case and the visible surface of which has features, wherein a soluble layer (2) of a photosensitive polymer is selectively deposited on said visible surface, the thickness of said soluble layer being at least equal to the height of said features, a first tie layer (3) of the Ti, Ta, Cr or Th type is vacuum-deposited by magnetron sputtering with a thickness of at least 100 nm by physical vapor deposition (PVD) on said surface thus selectively coated, followed, without venting atmosphere, by PVD deposition of said second layer (4) made of Au, Pt, Ag, Ni, Pd, TiN, CrN, ZrN or alloys thereof with a thickness of at least 100 nm, and then said soluble layer (2) is dissolved.
2. The process as claimed in claim 1, in which, before said soluble layer (2) is dissolved, an additional layer (5) of a noble metal or an alloy of noble metals is deposited by electroforming.
3. The process as claimed in claim 2, in which a thermoplastic polymer mask produced by thermoforming is applied to said photosensitive polymer layer (2).
4. A ceramic element intended to be fitted onto a watch case and the visible surface of which has features, wherein these features are fixed to this surface via a first Ti, Ta, Cr or Th tie layer (3) at least 100 nm in thickness, covered by at least one second layer (4) of the group comprising Au, Ag, CrN, Ni, Pt, TiN, ZrN, Pd or alloys thereof, with a thickness of at least 100 nm.
5. The ceramic element as claimed in claim 4, the shape of which is circular, the face forming said visible surface being of frustoconical shape.
6. The ceramic element as claimed in claim 4, the shape of which is that of a polygonal frame, that face forming said visible surface being of frustopyramidal shape.
7. The ceramic element as claimed in one of claims 4 to 6, in which said ceramic is ZrO₂, Al₂O₃ or a mixture of the two.
8. The ceramic element as claimed in one of claims 4 to 7, in which said features are formed by an additional layer (5) with a thickness of at least 0.10 mm, made of the same metal or alloy as said second layer (4).
9. A watch case comprising a ceramic element according to one of claims 4 to 8.