Determination of Director Distributions in Liquid Crystal Polymer-Films by Means of Generalized Anisotropic Ellipsometry

We report on how to achieve and measure director tilt angle distributions θ( z ) in cross-linked nematic liquid crystal polymer (LCP) films by means of generalized anisotropic ellipsometry. LCP-alignment is made by linearly photopolymerized (LPP)-photo-alignment of LCP films on single substrates. For the first time arbitrary tilt angle distributions are achieved and experimentally verified. It is shown that not only the birefringence Δ n of novel LCP-materials, which exhibit values up to Δ n =0.4, but also the tilt distribution θ( z ) of the LC director can be varied. θ( z ) is shown to be tunable between substrate surface and LCP/air interface over the entire range 90°≥θ≥0°. The control of the tilt distribution in thin LCP-films on single substrates is essential for many applications, for instance in LPP/LCP wide-view films designed to increase the field of view of liquid crystal displays (LCDs).