Improved Optical Properties of Transparent Low-Emissivity Coatings Using an Asymmetrical Structure Containing Two Silver-Alloy Layers

Transparent low-emissivity coatings of AlSiN/Ag99.1Mg0.5Eu0.4 alloy (1)/AlSiN/Ag99.1Mg0.5Eu0.4 alloy (2)/AlSiN films using the environmentally robust AgMgEu alloy and the AgMgEu-alloy (2) layer thicker than the AgMgEu-alloy (1) layer were developed. The optical properties of the films were improved when the second Ag-alloy layer was 1.2 to 2.0 times thicker than the first Ag-alloy layer. Specifically, they had a sharp cut-off for near-infrared light from the sun while retaining a high visible transmittance. A visible transmittance of 80% and a shading coefficient of 0.45, corresponding to a reflectance of 77% at a wavelength of 850 nm were realized for glass/AlSiN (47 nm)/AgMgEu (11 nm)/AlSiN (94 nm)/AgMgEu (18 nm)/AlSiN (47 nm) films.