A method for forming a distinctive background darker areas to bright metal surface and comprising in this way colored areas of the metal surface

摘要

PCT No. PCT/FI93/00433 Sec. 371 Date May 1, 1995 Sec. 102(e) Date May 1, 1995 PCT Filed Oct. 22, 1993 PCT Pub. No. WO94/11146 PCT Pub. Date May 26, 1994A method of providing by a laser beam on a bright metal surface (1) areas discernible from the surrounding surface as darker areas for producing for instance optically readable marks (5) and a metal surface provided in this manner. The procedure for producing marks not weakening the general properties of the metal surface is that the metal surface (1) is exposed to a laser beam pulse, the energy of which is 1 to 10 J/cm2, preferably 3 to 5 J/cm2 and the duration 5 ns to 1 mu s, preferably 15 to 30 ns; a spot of impact (7) of the laser beam pulse on the metal surface (1) is changed in such a way that a new spot of impact (8) overlaps the earlier spot of impact (7) and the metal surface (1) is exposed to a new laser beam pulse, such that an area (7a) of the metal surface, where the pulses do not overlap each other and which abuts on the spot of impact of the new pulse, gets a color contrasting with the original metal surface (1).