Patent DE-102008038118-A1 (DE)
Title: Removing layers applied on a transparent substrate with a laser beam, comprises passing the laser beam through a transparent substrate and then reaching the layers from the substrate side
Inventor: DU KEMING
IPC: B23K26/16
Filed: 2008-08-17
Abstract: The method comprises passing a laser beam (62) through a transparent substrate (11) and then reaching the layers from the substrate side. The wavelength of the laser beam is selected, so that the laser beam is not absorbed by the substrate such as glass or polymer and the absorption of the laser beam by the layer and/or the layer system is high, so that the layer and/or the layer system is removed. The removal process is caused in a single step process by the pressure generated by the absorbed laser energy in a first layer (L1) (12). The layer system is removed by multi-step process. The method comprises passing a laser beam (62) through a transparent substrate (11) and then reaching the layers from the substrate side. The wavelength of the laser beam is selected, so that the laser beam is not absorbed by the substrate such as glass or polymer and the absorption of the laser beam by the layer and/or the layer system is high, so that the layer and/or the layer system is removed. The removal process is caused in a single step process by the pressure generated by the absorbed laser energy in a first layer (L1) (12). The layer system is removed by multi-step process by using laser beam. A pulsed laser or Q-switched laser or mode-locked laser is used. The layer system is solar layers. The laser beam has a wavelength of larger than 1200 nm. The laser beam is produced by neodymium-doped laser, erbium-doped laser, thulium-doped laser, holmium-doped laser or optically parametric amplifier and/or oscillator. In the layer system, the laser energy absorbs by the first layer (L1). The pressure in the first layer is higher than the sum of the pressures, which are generated by the laser energy absorbed in the second layer (L2) (22) and third layer (L3) (32). The expansion energy in the first layer is larger than the binding energy of second, third and other layers. A two-stage process is used, where in the first stage, the second and third layers are removed by a first laser beam with a defined wavelength, which is not absorbed by the substrate and the first layer, and in the second stage, the first layer is removed with a second laser beam with a further wavelength, which is not absorbed by the substrate. The wavelength of the first laser beam lies in the visible region and the wavelength of the second beam is selected around 350 nm. The second harmonic around 670 nm from neodymium-doped laser, which is operated with the wavelength around 1340 nm, is used as first laser beam, and the fundamental around 1340 nm from the neodymium-doped laser is used as second laser beam, and/or the second harmonic from the neodymium-doped laser, which is operated with the wavelength around 1000 nm, is used as first laser beam, and the third harmonic from the neodymium-doped laser is used as second laser beam. An independent claim is included for a plant for removing layers applied on a transparent substrate with a laser beam.