15 July 1999 Photoinduced and grating alignment of polyimide using excimer lasers for liquid crystal displays
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Abstract
Recently there has been renewed interest in the grating alignment of liquid crystals because of its application in bistable nematic displays. In this paper, gratin and photoinduced liquid crystal alignment techniques based on excimer laser exposure of thin polyimide films are discussed. Gratings are etched into the alignment film using a KrF laser illuminated through a phase mask. These give homogeneous liquid crystal alignment with the liquid crystal directors aligned along the grooves of the grating. The observed azimuthal anchoring strength is compared with that predicted using Berreman theory. No pretilt is observed because of the grating symmetry. When a polarized excimer laser beam is incident on the film with a fluence below that required for ablation, an anisotropy is created photochemically by selective depletion of the polymer chains. Exposure of the polyimide with elliptically polarized light at non-normal incidence gives pretilted alignment. Grating etching followed by photoinduced alignment can be used to obtain pretilted grating alignment with a pretilt angle of 3 degrees.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Christopher J. Newsome, Mary O'Neill, Guy P. Bryan-Brown, "Photoinduced and grating alignment of polyimide using excimer lasers for liquid crystal displays", Proc. SPIE 3618, Laser Applications in Microelectronic and Optoelectronic Manufacturing IV, (15 July 1999); doi: 10.1117/12.352677; https://doi.org/10.1117/12.352677
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