Low emissivity coatings on architectural glass

Abstract New energy conservation regulations became effective in Germany by the beginning of 1995. These regulations contain stringent instructions on the thermal insulation of buildings, and thus imply the use of so-called “low emissivity” coatings for nearly any kind of architectural glazing. As a consequence, the new law has significant impact on the market for vacuum coating equipment, which nowadays plays a key role in manufacturing low emissivity thin film systems. Modern vacuum coaters handling panes of glass with dimensions of up to 3.21 m × 6.00 m operate at cycle times less than 1 min and provide uptimes that exceed 90% Novel solutions for high rate magnetron sputtering, the key process for large area coating, are presently under laboratory investigation or already successfully implemented into industrial coaters. AC powered magnetron systems permit the deposition of optical thin films with high rates and an outstanding process stability. Current development work on the design of low-e film stacks is aiming in highly transparent and chemically stable coatings permitting a heat transfer coefficient k of 1.0 W/m 2 K and less. The present paper tries to give an overview on the state-of-the-art related to vacuum coating of glass as well as low-e film designs and their properties.