New low emissivity coating based on TwinMag® sputtered TiO2 and Si3N4 layers

This paper presents the results of the recently developed silver based low emissivity coating on glass with sputtered TiO2 and Si3N4 layers using TwinMagTM. TwinMag technology can strongly influence thin film properties: (i) the substrate is continuously bombarded by positively charged high energetic ions, (ii) TwinMag technology allows the deposition of TiO2 films in the metallic mode of the cathode characteristic, leading to stable sputtering processes and the high deposition rates. This is of particular interest for large scale industrial applications. The new layer system comprises: Glass \ TiO2 \ Blocker \ Ag \ Blocker \ Si3N4 Titanium dioxide (TiO2) has a high index of refraction, which makes it an excellent material for low-E glass with high optical transmission. Furthermore, the TiO2 layers produced by the TwinMag process have very smooth surfaces. This improves the electrical conductivity of the silver film, thus gives more freedom when designing the optical properties of the final product. The top layer, Si3N4, is very hard which secures the excellent mechanical durability of the complete coating. Both the calculated results and experimental measurements show that the optical properties of the developed system are very stable, especially the colour appearance, i.e, a relative large change of the thickness of the first or last layer does not shift the colour co-ordinates of the produced coating notably. This property is of extraordinary interest in the industrial scale mass production. (C) 1999 Elsevier Science S.A. All rights reserved.