Dielectric behavior of polyvinyl alcohol (PVA) and its influence on LCDs

This paper describes how the polyvinyl alcohol (PVA) used to anchor molecules in nematic liquid crystal cells (NLCs) presents the typical behavior of a disordered solid whose electric conductivity is frequency and temperature dependent (sigma'(omega,T)), in accordance with the hopping behavior. It has also been found, however, that PVA used as alignment layers in liquid crystal displays (LCDs) causes dielectric interfacial dispersion in these displays. This interfacial polarization can be modeled in the intermediary frequency range (10-10(3) Hz), since neither liquid crystal nor PVA show, separately, a dielectric dispersion mechanism in this region. Thus, even though isolated PVA shows a hopping behavior, this behavior can be disregarded in the intermediate frequencies (10-10(3) Hz) in the analysis of LCDs.