24 October 2000 Liquid crystal polymers and networks for display applications
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Photopolymerization of liquid-crystalline (LC) monomers produces polymer films with a spatial control over the molecular organization. A powerful tool for creating even more complex molecular architectures than by LC order alone is photo-induced diffusion during polymerization of these monomers. Photo-induced diffusion during polymerization of chiral-nematic monomers yields a cholesteric network in which the helical pitch gradually changes over the cross-section of the film. The polarization selective reflection band can thus be made much wider than those of single pitch materials and may expand the whole visible spectrum. Performing photo- induced diffusion on a length-scale of half the cholesteric pitch by using a liquid-crystalline photoinitiator yields a cholesteric network with a deformed helix. Helix deformation gives higher order reflections and a built-in optical retardation. When the deformed helix is combined with a pitch gradient over the film thickness, the built-in retardation can be used for wide-band cholesteric polarizers that directly generate linearly polarized light without an additional quarter-wave foil.
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Dick J. Broer, Dick J. Broer, Jos A.M.M. Van Haaren, Jos A.M.M. Van Haaren, Johan Lub, Johan Lub, "Liquid crystal polymers and networks for display applications", Proc. SPIE 4107, Liquid Crystals IV, (24 October 2000); doi: 10.1117/12.405329; https://doi.org/10.1117/12.405329

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