Preparation And Properties Of Flexible Reflective Cholesteric Liquid Crystal Devices

Flexible displays are especially suitable for mobile phones, laptops, electronicbooks, electronic posters, automotive dashboards as well as car sensors because of itslight, thin, flexible and impact-resistant properties. Its flexible feature makes theproject design not only confined to be plane, but also have the diversified appearanceof the display mode. Due to Bragg selective reflection and bistable properties, LCDshave the advantages of low power consumption, without backlight, and long-timeimage saving in the power-off situation. In order to broaden the application of flexibleliquid crystal, the processes and properties of the flexible devices had been studied inthis thesis.Firstly, flexible cholesteric liquid crystal devices were prepared with ITO-PETfilms via perfusion method using spacers to control the thickness of devices. Effectsof processing parameters were investigated and optimized. The microstructure andmorphology of the devices were studied using Contact Angle Tester and Microscope,and the electrical properties of the devices using UltravioletvisibleSpectrophotometer(UVS). The results show that the inductive effect of the interfacecoating effectively improves the stability of the liquid crystal alignments. Thusflexible bistable cholesteric liquid crystal devices were obtained using spacers of6μmsize. The effective display area could reach10×15cm2with a transmittance of90%at550nm and a reflectivity of42%in the640nm.Secondly, gelatin and PVA were employed as the emulsifier and the influencesof emulsification conditions, vatious coating processes and raw material ratios wereanalyzed. In this way uniform, exquisite, stable liquid crystal emulsion was preparedat the conditions:40℃in the water bath, stirring speed2000rpm, emulsification time30min and addition of corresponding spacer. Then the flexible PSCT devices wereobtained with different thickness. Characterization results of the electrochromicproperties show that the thinner the device is, the lower the driving voltage.Finally, the properties and applications of devices prepared via prefusion methodwere studied. Results of device performance tests show that: the devices can work atthe temperature ranging from0to64℃, with a transform recycle between two steadystates of over40,000times under45V voltage driven; the devices are flexible and hasgood resistance to water, salt water and acid; Moreover, the effective display area of the devices can be enlarged through the device-coupling; a characteristic displayexperiment was carried out after treating the electrode with etching technology. Thedesired pattern of two steady states can clearly display with a long-term preservation.These indicate that the device can realize dynamic or static images display. Besides,the experiments of pressure-sensitive tablet were carried and the storage capabilitiesof the LCD was showed. The work provided a basis for future industrial applicationsof flexible device.