Colors in Reflection for Coated Windscreens

Carole Baubet, Jürgen Schütt and Nicolas Nadaud

Solar control coatings for windscreens offer numerous advantages, including a better thermal comfort and reduced air conditioning compared to standard products. However, automotive designers and final customers dislike the occurrence of red or violet color in reflection occurring at higher angles of observation. This paper presents a study of angular dependence of color in reflection based on numerical simulation and measurement on various real coatings.

An important initial conclusion is that some of the individual layers should be thickness-controlled almost at the atomic level (as fi ne as ±0,7 nm on a 10 nm layer thickness). The second finding is that the color change versus the incidence angle, is not only related to the color values (a*,b*) but also to the combination of the whole stack. This opens the way to design coatings which better address
market requirements, i.e. a neutral-blue or a greenish color in reflection, while minimising angular dependence of the color, especially avoiding the red reflection at high angle of observation.

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