COLOR OF DIELECTRIC CONDUCTIVE DOUBLE-LAYER FILMS DEPOSITED BY DRY-COATING PROCESSES

We have developed a continuous dry-coating process, which can provide stainless steel strips with multilayer ceramic or metallic film coatings. For example, a transparent overlayer of SiO2 is deposited onto an underlayer of TiN hard and colour coating on stainless steel sheet to increase corrosion resistance. However, the colour of such a dielectric-conductive double-layer coating has been known to change its colour tone depending on the film thickness of the overlayer. In this study, optical properties of double-layer films deposited by dry-coating processes were investigated and it was found that a model based on multiple reflection has enough accuracy to estimate the colour variation quantitatively. With this model, it is possible to calculate the optical reflectance spectra and the colours of double-layer coatings without empirical parameters. Results of the colour simulation by this method will be presented from a viewpoint of the optical design of decorative coatings.