Composite systems for display applications from cellulose elastomers and nematic liquid crystals

Composite systems made from cellulose derivatives solid films impregnated by a nematic liquid crystal can be used as electro-optical devices [H.V. Craighead, J, Cheng, S. Hackwood, Appl. Phys. Lett., 40 (1982) 22; M.H. Godinho, J.L. Figueirinhas, A.F. Martins, Liquid Cryst., 20(3) (1996) 373]. The electro-optical behavior of such cells depends on the nature of the cellulose derivative used, the nematic liquid crystal, the preparation conditions of the tells and of the cellulosic films, and the rugosity of the films' surface [M.H. Godinho, J.L. Figueirinhas, A.F. Martins. Liquid Cryst., 20(3) (1996) 373; M.H. Godinho, A.F. Martins, A. Almeida, J.L. Figueirinhas 16th International Liquid Crystal Conference, Kent USA, June 24-28, 1996]. Ln this work we study the influence of preparation techniques, number of polymer layers (1-3 layers each 9 mu m thick), thickness of the liquid crystal layer (8-18 mu m) and ageing (9 months), upon the electro-optical response of the cells, The cells used in this work were shown to exhibit high transmission coefficients (up to 82%) in the activated state and high contrast (up to 266). They also show good temporal stability and the cells' optical behaviour is strongly dependent on the number of films' layers. (C) 1998 Elsevier Science B.V.