Environmentally robust Ag–Cu based low-e coatings

Low emissivity (low-e) coatings minimise heat transmittance through the coating and emission of infrared light from hot surfaces. They are used in space applications to reduce overheating of the spacecraft, in architectural applications and automotive windows to block heat from entering a building or vehicle. Typically, in window applications the low-e coatings consist of a multilayer coating, which combine metallic films (approx. 10 nm); responsible for the heat reflection and dielectric films (approx. 40 nm); used to protect the metallic films and enhance their visible transmittance. Commercially available low-e coatings can contain more than 15 layers, with Ag typically used as the metallic layer. However, Ag is soft and tends to tarnish, making Ag-based low-e coatings vulnerable to degradation when exposed to environmental conditions. In this study we demonstrated environmentally durable low-e coatings based on Ag–Cu alloyed thin films. The thin film alloys showed higher level of scratch resistance than conventional pure Ag coatings with high level of transmittance of visible light. The multilayer coating consisting of a dielectric film, metal alloy film and a protective coating was demonstrated as robust, long-life, first surface low-e coating.