Method for manufacturing a ceramic-based external horological or jewellery part with patterned decoration
A method for manufacturing an external horological or jewellery part including the following successive steps of producing a base plate in a substrate made of a ceramic material, mirror polishing the base plate on at least one face, referred to as the “display face”, intended to be visible to a user, laser machining according to predefined patterns in a preliminary step, oxidising the base plate by heat treatment.
1 . A method for manufacturing a dial of a timepiece, the method consisting of, in order, steps of:
producing a base plate in a substrate made of a ceramic material, the base plate having a thickness between 0.1 mm and 1.2 mm,
directly after producing the base plate, mirror polishing the base plate on a display face of the dial to be visible to a user such that the base plate has a shiny appearance,
directly after the mirror-polishing step, laser machining predefined patterns having a matte appearance on the mirror-polished display face, wherein a surface area of the patterns represents between 40% and 60% of a surface area of the display face and the patterns have a depth between 5 μm and 10 μm,
directly after the laser-machining step, oxidizing, by heat treatment, the laser-machined, mirror-polished base plate at a temperature between 500 and 1,000 degrees Celsius;
depositing a transparent or semi-transparent thin layer on the display face, after the oxidizing step; and
depositing a thin layer on a bottom face of the base plate opposite the display face, after the oxidation step, to opacify the substrate,
wherein, in the machining step, the predefined patterns are obtained by digital image processing, so as to obtain a digital image formed of black pixels and white pixels, said black pixels or white pixels representing the predefined patterns,
wherein a graphic content of the digital image includes a dendritic shape, such that the patterns machined on the base plate give the base plate a frosted appearance.
2 . The manufacturing method according to claim 1 , wherein the base plate is made of a zirconium oxide substrate.
3 . The manufacturing method according to claim 1 , wherein the base plate is made of glass, stone, alumina, or sapphire.
4 . The manufacturing method according to claim 1 , wherein, in the machining step, the image obtained is formed of black pixels, white pixels, and greyscale pixels, said black, white, and greyscale pixels representing the predefined patterns.
5 . The manufacturing method according to claim 4 , wherein a shade of grey of the pixels is representative of the depth of machining.