Ruth A. Mendonsa
Glass has traditionally been the material of choice for automobile headlamp cover lenses, but it poses severe limitations to design flexibility and creativity. While synthetic materials such as plastic would make cover lenses lighter and would allow a wider range of designs, its susceptibility to heat damage from a halogen light source presents a problem.
Balzers' heat-resistant ITO coating opens the way to synthetic optics design flexibility.
Docter Optics GmbH, an OEM supplier of lenses used in the projection systems of headlamps and antifog lamps for the automotive industry, approached Balzers Thin Films regarding the possibility of developing a heat-resistant coating for its lenses for automobile headlamps. The use of its products for the automotive industry was new territory for the coating manufacturer, but it was intrigued with the idea.
Meeting the challenge
The project presented some interesting challenges to Balzers. The newly designed headlight systems, comprising a small reflector and a lens, could not be treated the same way as those for optical instruments that the company was used to treating. The coating had to keep the temperature of a dirty synthetic lens below a certain temperature, depending on the material used. In addition, Docter Optics required a zero-defect rate for its deliveries -- quality requirements much higher than those of other clients. After many attempts, Balzers produced a coating that met all of the specifications. Dubbed ITO coating, its benefits include high transmission in the visible and optimal heat suppression for halogen lamps.
The coating is now being applied to a car industry high-volume product. Balzers expects to coat 500,000 lenses in 1999. Jens Fischer, director of the automotive components business unit at Docter Optics, says the round 60- to 70-mm-diameter lenses are being used on such cars as the new Volkswagen Beetle, the Mercury Cougar, Cadillac Seville and Chrysler LHS.
According to Peter Enders, sales manager at Balzers, ITO coating has found its way to other applications where heat poses a problem, including surgical lighting, studio illumination and food illumination.