Process solutions for the vacuum thin-film coating of three-dimensional partsProcesses for durable reflectors on complex shaped parts
The main applications for vacuum metallization of three-dimensional parts are reflectors and decorative bezels for automotive head lamps, indicators and tail lamps. They are subject to both permanent design changes and increasing technical complexity, for instance due to the development of brighter light sources, from halogen bulbs and Xenon discharge lamps to LEDs and lasers.
Naturally, there are other applications – mirrors, electronic device housings, cosmetics casings and, of course, lamps for vehicles such as bicycles and airplanes as well as road and domestic lamps and many more.
Vacuum metallization for reflection and decoration
Reflectors and decorative coatings have a common basic layer sequence:
First, the substrate surface is prepared for optimal adhesion of the following metal coating through a plasma pretreatment process. Next, a metal layer – usually high-purity aluminum – is deposited via either thermal evaporation or magnetron sputtering.
Automotive lamps are exposed to a wide range of temperatures and humidity over a car's lifetime. To prevent corrosion of the reflective layer, a thin, transparent protection layer is required. This is done via plasma polymerization of a siloxane precursor.
Finally, the surface energy of the coating can be modified to perfectly fit the individual application: Hydrophilic coatings improve glue adhesion when assembling the cover lens of a lamp and reduce hazing on humid mornings, while a hydrophobic finish helps to keep trim parts or housings free of finger prints.
Efficient processes for efficient coaters
The process steps described above have been widely used throughout the vacuum coating industry for decades. Bühler Leybold Optics' decades of experience enables us to tailor the coating solution to the individual customer's needs. One particular challenge is the coating of three-dimensional substrates, since coating thickness will vary significantly at different positions of each substrate. This is minimized by moving substrates during the coating processes as well as by optimizing process parameters and coating source designs.
Special attention is paid to making each individual step as fast as possible for economic mass production, while at the same time ensuring highest coating quality and production stability.