Liquid Crystal Materials for Matrix Displays.
Abstract
Studies were made on liquid crystal (LC) and display cell materials related to the operation of MOSFET matrix displays in the dc-activated dynamic-scattering (DS) mode at elevated temperatures. Thermal degradation of ester LCs was accelerated by soft glass surfaces, which increase hydrolysis-type reactions. Pyrex, quartz, and coatings such as Si02, Si3N4, indium tin oxide (ITO), and polyvinyl alcohol (PVA) on soft glass (e.g., float glass) gave less thermal degradation at 100 C than uncoated float glass or drawn glass. Hermetically sealed cells were necessary for long term thermal stability of ester LCs, although degradation occurs even in sealed cells when the LC is in direct contract with soft glass. Long term LC stability was observed at 100 C in sealed cells with ITO/PVA coatings on float glass. However, the epoxy type sealants previously used introduced harmful conductivity impurities into the LCs aT elevated temperatures. These caused very limited dc lifetime, even at only 55 C and in the presence of redox dopants. An ultraviolet-cured optical cement was found to be a much better sealant; at 100 C it introduced two orders of magnitude fewer conductive impurities into ester LCs and caused less surface alignment changes than epoxy sealants. Studies on new ester LC mixtures with relatively low viscosity showed excellent dc-DS characteristics.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1982
- Accession Number
- ADA114444
Entities
People
- Anna M. Lackner
- J. David Margerum
Organizations
- HRL Laboratories