Improved Materials for DC Dynamic Scattering at Elevated Temperatures

Publisher Website
Google Scholar
Abstract
Liquid crystal (LC) mixtures and a sealant suitable for dc-activated dynamic scattering (DS) matrix displays are developed for wide range storage temperature (−60 to 80°C) and for elevated temperature operation. Three improved eutectic nematic mixtures are formulated with nematic ranges (undoped) of 0 to 74, −;4 to 82, and −13 to 78°C, with flow viscosities of 31, 32 and 36 cP respectively at 25°C. Several types of sealants are tested in contact with LC and are evaluated according to the level of contamination they introduce at elevated temperature. One UV-curved sealant shows no apparent degradation effects after more than 1800 hours of 100°C heating with an undoped ester LC in a vacuum-filled test cell made with this sealant. Thermal storage stability at 80°C and low temperature stability at −60°C in such sealed cells show little change in surface alignment, resistivity, and DS characteristics in LCs with redox dopants, namely dialkylferrocene and (2,4,7-trinitro-9-fluorenylidene)-malononitrile. The LC materials with this redox dopant also show good thermal stability for over 1100 hours at 100°C in evacuated glass ampoules. Elevated temperature dc-DS stability with 20 V dc at 55°C shows more than 5000 hours for two of the new redox-doped LC mixtures in sealed transparent cells. The viscosity, dielectric anisotropy, conductivity anisotropy, and dc-activated DS effects are studied as a function of temperature for one of the mixtures. Response times of DS as a function of temperature (25° to 65°C) and cell thickness are also studied.

This publication has 9 references indexed in Scilit: