Method for marking a sapphire watch crystal

Patent metadata

Field	Value
Publication number	US-11320790-B2
Application number	US-202016819400-A
Country	US
Kind code	B2
Filing date	Mar 16, 2020
Priority date	Mar 19, 2019
Publication date	May 3, 2022
Grant date	May 3, 2022

Abstract

A method for marking a sapphire watch crystal, through the interaction between a laser beam and the sapphire. The beam is focused on a point inside the crystal and the interaction is such that it produces a rectilinear opaque area, which is parallel to the upper surface of the crystal or perpendicular to the surface. The orientation of the opaque area depends on the mode of operation applied. According to the hatching mode of operation, the beam is scanned along one or more linear paths, producing opaque lines inside the crystal, which are parallel to the upper surface. The perforation mode of operation produces distinct opaque areas, obtained by discontinuous operation of the beam on a number of juxtaposed points. According to this latter mode of operation, the opaque areas extend in the direction perpendicular to the upper surface of the crystal.

First claim

The invention claimed is:

1. A method for marking a sapphire watch crystal, the crystal having a plane upper surface and a lower surface, the method comprising:
using a laser beam directed perpendicularly to the upper surface;
focusing the laser beam at a point inside the material of the crystal, wherein an interaction between the laser and the sapphire at the focal point produces a rectilinear opaque area which extends along a path in a direction parallel to the upper surface or in a direction perpendicular to said upper surface;
forming a plurality of parallel rectilinear opaque paths with the laser beam which extend in the direction parallel to the upper surface or in the direction perpendicular to said upper surface, in order to mark a first portion of the crystal in a first hatching step,
wherein the laser beam is scanned at a scanning speed between 2 m/s and 3 m/s, and
wherein a distance between each of the plurality of parallel rectilinear opaque paths is 10 μm to 20 μm.

2. The method according to claim 1 , wherein the laser beam is scanned along a linear path while remaining focused on a point at a fixed distance with respect to the upper surface of the crystal, and
wherein said plurality of parallel rectilinear opaque paths are essentially parallel to the upper surface of the crystal.

3. The method according to claim 1 , wherein a second hatching step is performed in a transverse direction with respect to the first step, the second step being performed on a second portion of the crystal, which at least partially covers the first portion, the second hatching step being performed at the same distance respect to the upper surface as the first hatching step.

4. The method according to claim 1 , wherein several hatching operations, comprising one or two steps, are performed at successive levels in the material, in order to obtain a three-dimensional marking, and wherein the rectilinear opaque areas formed at two adjacent levels are separate from each other.

5. The method according to claim 2 , wherein parameters of the laser beam are as follows:

Type of laser
Pulse laser

Pulse length
200 fs-10 ps  

Wavelength
500 nm-1200 nm

Pulse frequency
200 kHz-1.5 MHz 

Laser energy
1 μJ-20 μJ.

6. The method according to claim 2 , wherein geometric parameters are defined as follows:

Depth of the laser focal point
0.5 mm-1 mm.

7. The method according to claim 1 , wherein the laser beam is focused consecutively on a plurality of juxtaposed points located at the same distance from the upper surface, and wherein the rectilinear opaque paths are produced at each of the points, said areas extending in the direction perpendicular to the upper surface.

8. The method according to claim 7 , wherein several marking steps are performed at successive levels in the material, in order to obtain a three-dimensional marking, and wherein the rectilinear opaque areas formed on two adjacent levels are separate from each other.

9. The method according to claim 7 , wherein values of laser parameters are as follows:

Type of laser
Pulse laser

Pulse length
200 fs-10 ps  

Wavelength
500 nm-1200 nm

Pulse frequency
200 kHz-1.5 MHz 

Laser energy
1 μJ-20 μJ

Laser on time
0.01 ms-0.1 ms. 

10. The method according to claim 7 , wherein values of geometric parameters are defined as follows:

Distance between two adjacent
0.01 mm-0.03 mm

points

Depth of the laser focal point
0.5 mm-1 mm.

11. The method according to claim 1 , wherein the upper surface of the crystal is provided with an anti-reflective layer.

Assignees

• Comadur Sa

Inventors

• Netuschill Alexandre

Classifications

• B23K26/364

  for making a groove or trench, e.g. for scribing a break initiation groove · CPC title

• G04B39/006 Primary

  out of wear resistant material, e.g. sapphire · CPC title

• G04B45/0084

  Pictures or inscriptions on the case or parts thereof, attaching complete pictures (decoration and manfuacture thereof G04B45/0076; special decorative parts which are attached to the case or other parts G04B47/04) · CPC title

• B23K26/50 Primary

  Working by transmitting the laser beam through or within the workpiece · CPC title

• B41M5/262

  recording or marking of inorganic surfaces or materials, e.g. glass, metal, or ceramics (marking of plastic artifacts with inorganic additives B41M5/267) · CPC title