Study On The Preparation Of Liquid Crystal Microcapsules And Their Applied Performances In Displays

As the key technology for LCs applications, liquid crystal display (LCD) is one of themost important display technologies at present. Rapid social development is pushingforward the boundary for more advanced display technologies. From the perspective ofnew functions and market competition, applying cholesteric liquid crystal (CLC) toachieve reflective, bistable, and flexible color display will become the new trend ofLCD development, which is also an important developing direction of the wholedisplay field.In this dissertation, to effectuate a reflective, bistable, flexible, and colorful LCD,microencapsulated methods were employed to disperse, stabilize, and protect the LCs,and the final products were employed to fabricate rigid and flexible polymer-inducedstabilized cholescteric texture (PSCT) devices. In the same work, the display propertiesof LC microcapsules, the electro-optical characteristics of the displaying devices, andthe fabrication process for the thin film devices were investigated.First, LCs were microencapsulated with poly(mehyl methacrylate)(PMMA) viasolvent evaporation method, with gelatin-gum arabic (Gelatin-GA) via corcervationand with UF-resin via in-situ polymerization. By analyzing the morphology, content,and particle diameters and distributions of the microcapsules, we determined theoptimal conditions applied to the current preparation system, including the reactiontemperature, agitation rate, material content, and co-agents. The work also confirmedthat the intrinsic structure of LC was not damaged through the microencapsulatedprocesses mentioned above.Second, I have studied the optical properties of the LC microencapsulatedproducts. It is confirmed that the microcapsules have transparent shells when usingPMMA, Gelatin-GA, and U-F as the polymer materials; the desired particle size forCLC microcapsule displaying vivid color should be2to30μm; spherical CLCmicrocapsules can exhibit multi-color and are not suitable for the fabrication of PSCTfilms, while the flattened spherical CLC microcapsules just show a section with vivid color and are feasible of making PSCT films. By analyzing the multi-color display ofCLC microcapsules, an alignment model of LC molecular was set up and discussed.The relationship between microcapsule morphologies and its optical properties werethus confirmed theoretically.Finally, PSCT thin films were fabricated from CLC microcapsule products. ACLC display device was built by incorporating the film between two transparentelectrodes afterwards. Being driven under stable direct current, the device was able tohave reflective, bistable, and colorful displays. Using ITO glasses as the electrodes andcontrolling the PSCT film thickness as8μm, a rigid flat display device was obtainedwith the driving voltage of about40V. While using ITO/PET films as the electrodesand controlling the PSCT film thickness as8μm, the flexible display device had thedriving voltage of about45V.