Abstract
AbstractThe optical properties of the azo‐dyes SD‐1/SDA‐2, which are used for photoaligning of liquid crystals (LCs), are investigated with Variable Angle Spectroscopic Ellipsometry (VASE). Films of mixture of SD‐1/SDA‐2 are deposited by spin coating on silicon wafers. The estimated thickness is approximately 10 nm. To achieve photo‐induced anisotropy, one of the samples is illuminated during 15 minutes with linearly polarized UV light followed by thermal stabilization during 1 hour at 150 °C. VASE measurements are performed in the wavelength range 200–1350 nm at several angles of incidence and at different sample orientations. Dielectric functions of azo‐dye films without/with polarized UV light illumination were modelled using an ensemble of Lorentz oscillators. The results confirm the diffusion model proposed recently for explanation of the formation of the photo‐induced order in azo‐dye films under the action of polarized light. Refractive indices, their wavelength dispersion and thicknesses of films of SD‐1/SDA‐2 are reported here. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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