Effect of surface roughness on the optical properties of multilayer polymer films

Results of the influence of the surface roughness on the optical transmittance and on the interference spectral fringes produced by reflection of parallel layers of multilayer polymer films are reported. Samples studied were multilayer materials for graphic arts, obtained by spreading adherent emulsion layers over both sides of a substrate of polyethyleneterephatalate (PET) film with different surface roughness. The range of wavelengths of radiation studied is from 320 to 2500 nm, i.e. covering the ultraviolet and visible (UV–Vis), near-infrared (NIR) and infrared (IR) spectra. Strong correlations between spectral parameters of the optical transmittance and surface roughness were found, showing that these spectroscopical techniques are good complementary ways to study the surface characteristics of these engineering materials.