Photocontrollable Resistivity Change in Nanoparticle-Doped Liquid Crystal Alignment Layer: Voltage Holding and Discharging Properties of Fringe-Field Switching Liquid Crystal Modes

초록

In liquid crystal (LC) displays, deriving an optimum resistance level of an LC alignment polyimide (PI) layer is important because of the trade-off between the voltage holding and surface-discharging properties. In particular, to apply a power-saving low-frequency operation scheme to fringe-field switching (FFS) LC modes with negative dielectric LC (n-LC), delicate material engineering is required to avoid surface-charge-dependent image flickering and sticking problems, which severely degrade with lowering operation frequency. Therefore, this paper proposes a photocontrolled variable-resistivity PI layer in order to systematically investigate the voltage holding and discharging properties of the FFS n-LC modes, according to the PI resistivity (rho) levels. By doping fullerene into the high-rho PI as the photoexcited charge-generating nanoparticles, the rho levels of the PI were continuously controllable with a wide tunable range (0.95 x 10(15) omega center dot cm to 5.36 x 10(13) omega center dot cm) through Ar laser irradiation under the same LC and LC alignment conditions. The frequency-dependent voltage holding and discharge behaviors were analyzed with photocontrolled rho variation. Thus, the proposed experimental scheme is a feasible approach in PI engineering for a power-saving low-frequency FFS n-LC mode without the image flickering and image sticking issues.

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