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Abstract

Multilayer coating for polycarbonate substrate used as glass substitute essentially consisting of silicon, carbon, nitrogen, oxygen and hydrogen, characterized by a first anti-ultra-violet layer consisting of silicon, oxygen and/or nitrogen, carbon and hydrogen, according to formula: SiCx.sub.1 Oz.sub.1 Ht.sub.1, where x.sub.1 +z.sub.1 +t.sub.1 is between 1,2 and 1,5 SiCx.sub.1 Ny.sub.1 Ht.sub.1, where x.sub.1 +y.sub.1 +t.sub.1 is between 1,2 and 1,5 SiCx.sub.1 Ny.sub.1 Oz.sub.1 Ht.sub.1, where x.sub.1 +y.sub.1 +z.sub.1 +t.sub.1 is between 1,2 and 1,4 and t.sub.1 is always between 0,1 and 0,7; x.sub.1 before y.sub.1 and/or z.sub.1 is small, so that the limit of optical absorption is concentrated at about 350 nm; the second transparent hard layer consists of silicon, oxygen, nitrogen, carbon and hydrogen, of formula SiCx.sub.2 Ny.sub.2 Oz.sub.2 Ht.sub.2, where, in particular: either y.sub.2 =0, z.sub.2 is between 1,7 and 2,0, t.sub.2 is between 0,1 and 0,7, x.sub.2 before z.sub.2 is small; or y.sub.2 is between 1,0 and 1,3, t.sub.2 is between 0,1 and 0,7, x.sub.2 and z.sub.2 before y.sub.2 are small. The invention finds application in the protection of polycarbonate against aging caused by ultra-violet radiation, in particular for glasses of automobile headlights, spectacle glasses.

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First Claim