Characteristics of voltage holding ratio and residual direct current voltage for polymer-sustained-alignment liquid crystal cells formed from mixed monomers containing biphenyl- and benzilketal-groups

Abstract

For improving process efficiency of polymer-sustained-alignment liquid crystal displays (PSA-LCDs), new photo-initiation monomers (PI-monomers), 2-methoxy-2-methacryloyl-oxy-ethoxy-2-phenylacetophenon (2-MMOEP) and 2,2-dimethacryloyl-oxy-ethoxy-2-phenylacetophenon (2,2-DMOEP), were developed and investigated image sticking characteristics. LC cells having PSA layers formed from a monomer 4,4′-dimethacryloyl-oxy-biphenyl (4,4′-DMABiph) and each PI-monomer were fabricated, and voltage holding ratio (VHR) and residual direct current voltage (VrDC) were clarified as the image sticking characteristics. The VHR and the VrDC were improved with the LC cells having the PSA layers formed from 4,4′-DMABiph and 2,2-DMOEP owing to large rate constant of polymerization. In contrast, the VHR and the VrDC were deteriorated with the LC cells having the PSA layers formed from 4,4′-DMABiph and 2-MMOEP. The deterioration of the VHR and the VrDC was derived from the increase in the concentration of radical and/or ion generated from 2-MMOEP. The results indicate that the number of polymerizable group in the PI-monomer is important, and plural number of polymerizable group in the PI-monomer leads to high VHR and low VrDC.