Better aluminium mirrors by integrating plasma pretreatment, sputtering, and plasma polymerization for large-scale car headlight production

The move to abandon lacquering in today's car manufacture has revealed new challenges at the plastic interface, especially reduced adhesion of the coating and outgassing (mainly water) that can affect the aluminium quality. Under the increased temperatures inside head and fog lights, further outgassing often leads to hazy appearance of the reflector or the front lens by droplet condensation. These problems can be solved by a process sequence that includes some oxidizing plsama pre-treatment that ensures good bonding of the Al to the plastic and also enhances desorption of water. In addition, some plasma-polymerized adhesion-promoting base coat (if required, also desorption blocking) may be deposited. After Al deposition, first a corrosion protective layer and finally, a hydrophilic coating that suppresses hazing effects by spreading out any condensing vapors to some optically neutral layer are deposited.