Nanoplasmonic (“Sub-Critical”) Silver as Optically Absorptive Layers in Solar-Control Glasses

Triple-silver coated glasses, such as Vitro’s Solarban® 70XL glass, block nearly all the solar infrared of the electromagnetic spectrum, thereby providing excellent solar-control properties at high luminous transmittance. However, in order to reach even better solar-control performance demanded by increasingly stringent building codes, it is necessary to reject some portion of the visible spectrum. When a high luminous reflectance is unacceptable, the only option is to attenuate visible light via absorption. Vitro’s “sub-critical silver” technology employs a discontinuous layer of silver nanoparticles having plasmonic excitations which exhibit an absorption resonance in the visible. When used in coatings also employing continuous silver layers (which provide infrared reflective functionality) and dielectric layers (which protect the silver layers and serve as phase adjustment layers), such nanoplasmonic silver layers provide additional degrees-of-freedom to tailor product performance and aesthetics. Furthermore, this sub-critical silver approach is less prone to the formation of lightscattering centers (“haze”) as a result of post-deposition heat treatment. The first applications of nanoplasmonic silver were in Solarban R100 glass and Solarban 67 glass. In 2015, PPG Flat Glass (now Vitro Architectural Glass) introduced its latest flagship product, Solarban 90 glass, which employs three continuous silver layers and one nanoplasmonic silver layer.