Improvement of image sticking on liquid crystal displays with polymer layers produced from mixed monomers

Abstract

As a model of polymer-sustained-alignment liquid crystal display (PSA-LCD), the LC cells having the polymer layers produced from the homopolymers and copolymers of 4,4ʹ-dimethacryloyl-oxy-biphenyl (4,4ʹ-DMABiph) and 2,6-dimethacryloyl-oxy-naphthalene (2,6-DMANaph) were prepared and investigated image sticking phenomenon with evaluations of residual direct current voltage (VrDC) and difference in pre-tilt angle before and after application of alternate current (AC) voltage (Δtilt). The VrDC was effectively improved by adding a small amount of 2,6-DMANaph to 4,4ʹ-DMABiph because the concentrations of radicals and ions in the LC layer were decreased due to increase in the rate constant of the polymerisation with the addition of 2,6-DMANaph under UV light exposure. The Δtilt was proportionally increased with increasing the weight ratio of 2,6-DMANaph in the mixed monomers of 4,4ʹ-DMABiph and 2,6-DMANaph. We confirmed that the range of the weight ratio for 2,6-DMANaph in the mixed monomers of 4,4ʹ-DMABiph and 2,6-DMANaph from 10 to 25 wt% was useful for obtaining the small level of image sticking in the PSA-LCD.