Glazing

GLAZING Field of the invention The present invention relates to glazings which, in particular, may be used in solar collectors. In the present text, the term "glazing" means any material, e.g. glass or polycarbonate, transparent to visible electromagnetic radiation. Summary of the invention An object of the present invention is to provide a colored reflection from a glazing, e.g. from the cover glass of a solar collector. This approach has the advantage to separate the functions of optical selectivity and colored reflection, providing thereby more freedom to layer optimization. In addition, if the invention is used in a solar collector, the black, sometimes ugly absorber sheet is hidden by the colored reflection of the glazing. The principle of the invention relates to a thermal solar collector wtih a colored coating applied to the glazing. The coating reflects a color, thus hiding the corrugated absorber sheet,. However the complementary spectrum is transmitted. No absorption occurs in the coating. The coating can be deposited onto the inner of the glazing, as shown in the drawing, but also on the outer side, or on both. Also, a colored coating on the inner side can be combined with a mat outer surface (or with a diffusing substrate).The glazing can consist e.g. of white glass (low iron content), or of organic material such as polycarbonate. No energy should be lost by absorption in the coating. All non-reflected energy should be transmitted. Those objectives are achieved with the glazing according to the present invention which, preferably but not exclusively, comprises multilayer interference stacks of transparent materials. For the present invention the material choice must be realistic, and the considered refractive indices have consequently to be within a certain range. In addition to that, the maximum number of layers is limited. In contrast to applications such as laser interference filters, solar applications employ typically large surfaces to be coated at low price, which implies that production costs limit the number of individual layers building up the multilayer stack.