Study Of The Electro-optical Devices Based On Liquid Crystal

Liquid crystal display (LCD) technology which is widely used in the field of display has become one of the most important display technologies. Meanwhile, liquid crystal exhibits very promising applications in electronic paper and controllable light valve due to its particular structure and properties. Moreover, LCD technology plays an important role in the research and development of flexible devices in virtue of its relative maturity. In order to broaden the application fields of liquid crystal, electro-optical devices based on liquid crystal were centred on in this thesis. The processes and properties of the devices had been studied which were divided into three parts.Firstly, polyethylene (PE) thin film was chosen as the substrate and transparent electrodes with PEDOT as the conductive material were prepared. First, The wetting ability of the film to water had been increased through the combination of coronatreatment and surface modification, which make the contact angle decrease from 104.2°to 55.21°. Second, the conductivity of the layer had been raised through secondary doping of DMSO into PEDOT emulsion. We fabricated the PE thin film electrode by screw coating and the influence of transmittance and conductivity by layer thickness had been studied. The transparent film electrode we made has mean transmittance in visible and infrared region are more than 70% and 60% respectively.Secondly, the preparation process and properties of Polymer Stabilized Cholesteric Texture (PSCT) devices were investigated. First, we determined the―dry method‖for rigid cell and―wet method‖for flexible cell through explorations of the processes. At the same time, through the mixing of different amount of cholesteric liquid crystal and chiral dopant CB15, we get many liquid crystal mixtures with different central reflection wavelength, which exhibited different coloured states. PSCT devices were made by filling method and factors that may affect the electro-optical properties of PSCT as polymer concentration and cell gap have been mainly investigated. In conclude, the PSCT device with 4.07% or 6.07% liquid crystal concentration and 6μm cell gap exhibits low threshold voltage under 30V. Thirdly, Polymer Dispersed Liquid Crystal (PDLC) which based on scattering had been studied. Polymerization induced phase separation had been applied to prepare PDLC devices and polymer concentration and cell gap which could affect the electro-optical properties of the devices were investigated. The optimum conditions were 40% polymer concentration and 9.8μm cell gap which had a high contrast ratio of 7.8.Finally, we made a tentative fabrication of flexible devices of PDLC and PSCT, which also exhibit some electro-optical properties. But the process needs to be improved.