Laser-markable polymers and coatings
The present invention relates to laser-markable polymers and coatings which are distinguished by the fact that they comprise tin/antimony oxide-coated spherical TiO 2 particles of defined particle size as laser additive.
1. A method for the production of darkened laser-markings on a laser-markable polymer or on a laser-markable polymeric coating, which comprises:
laser-treating the polymer or polymeric coating, which polymer or polymeric coating comprises a polymer and, in the polymer, a laser additive, which laser additive comprises spherical TiO 2 particles which are coated on the surface with an antimony-doped tin dioxide layer (Sn,Sb)O 2 and the TiO 2 particles have a number weighted particle size of <15 μm, measured at the D 95 by means of laser diffraction, and
wherein, in the resulting polymer or polymeric coating, the laser-treating results in reducing the TiO 2 in the laser additive to Ti x O y , which results in a visibly darkened marking with a surface which is not roughened, where it was laser-treated.
2. The method of claim 1 , wherein the content of antimony in the tin dioxide layer is 0.1-60 mol %, based on the tin dioxide.
3. The method of claim 1 , wherein the laser additive has a number-weighted particle size of ≥0.05 μm, measured at the D 25 by means of laser diffraction.
4. The method of claim 1 , wherein the laser additive is employed in a concentration of 0.005 to 30% by weight, based on the polymer or polymeric coating.
5. The method of claim 1 , wherein the polymer is a thermoplastic, thermoset, elastomer or silicone.
6. The method of claim 1 , wherein the polymer additionally comprises one or more coloured pigments and/or dyes.
7. The method of claim 1 , wherein the content of antimony in the tin dioxide layer is 2-15 mol %, based on the tin dioxide.
8. A moulding composition, a product, a part or a film, which comprises a dark laser-marking on a polymer or polymeric coating thereof, which marking was produced by the method of claim 1 .
9. A powder coating, which comprises a dark laser-marking thereon, which marking was produced by the method of claim 1 .