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

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Abstract
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 Δn of novel LCP-materials, which exhibit values up to Δn=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).