Optical article having directional micro- or nanostructured thin film coating, and its process

Method of manufacture of an optical article comprising a substrate with a front main face and with a rear main face, at least one of the main faces being coated with a columnar micro- or nano-structured coating, wherein

• the substrate and the optical article are transparent or can be put in a state where they are transparent in at least a part of the visible region ranging from 380 to 780 nm, along at least one incidence angle;
• said columnar micro- or nano-structured coating comprises at least an array of contiguous columns comprising each a core and an upper layer covering said core, the core and the upper layer being structurally and/or chemically different and wherein said core and/or upper layer have light absorbing properties or can be put in a state where they have light absorbing properties with an extinction coefficient “k” equal to or higher than 10−2 in at least a part of the light spectrum ranging from 250 to 2500 nm;
• the method comprising the following steps:
• (a) depositing on the at least one main surface of the substrate, the core by physical directional deposition to create the array of contiguous columns;
• (b) depositing, on the core of the columns, at least one—upper layer by atomic layer deposition;
• the parameters of the deposition of the core and of the upper layer being controlled so as to provide a change in transmission or reflection of incident light through the optical article as a function of the angle of incidence of light,
• wherein the core of the columns has a porosity that is equal to or higher than.30%.