COMPOSITE SYSTEMS FOR DISPLAY APPLICATIONS FROM CELLULOSE ELASTOMERS AND NEMATIC LIQUID-CRYSTALS

Composite systems made from cellulose derivatives solid films impregna ted 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 t he 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. Figueirinh as, A.F. Martins. Liquid Cryst., 20(3) (1996) 373; M.H. Godinho, A.F. Martins, A. Almeida, J.L. Figueirinhas 16th International Liquid Cryst al Conference, Kent USA, June 24-28, 1996]. Ln this work we study the influence of preparation techniques, number of polymer layers (1-3 lay ers 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 ce lls, The cells used in this work were shown to exhibit high transmissi on coefficients (up to 82%) in the activated state and high contrast ( up to 266). They also show good temporal stability and the cells' opti cal behaviour is strongly dependent on the number of films' layers. (C ) 1998 Elsevier Science B.V.