| Polymer dispersed liquid crystal(PDLC)films consist of a liquid crystal(LC)material dispersed within a semi-continuous polymer matrix.PDLC are potentially useful for a variety of electro-optical applications including light valves,switchable windows,flexible large-area displays and other devices because they do not require polarizers and alignment layers.In this thesis,the thiol/acrylic ester matrix based PDLC materials are studied.observed the micro-structure of the polymer matrix taking away the LC component under scanning electron microscopy(SEM),measured the electro-optical properties of the PDLC films and the transmittance of the PDLC films in the wavelength range from visible(VIS)region to near infrared(NIR)region with LCD parameters tester and UV-VIS-NIR spectrophotometers,respectively,then optimized the electro-optical properties of PDLC films experimentally and theoretically.The main research contents are as follows:(1)The PDLC film via a one-step fabrication technique based on hotopolymerization of the thiol-acrylatereaction was successfully prepared.The morphology and electro-optical characteristics were investigated.The experimental results showed that it is possible to regulate the LC domain size and optimize the electro-optic properties of PDLC films by adjusting the LC content?thiol monomer functionality and content.Lower driven voltage and higher contrast ratio were achieved.(2)A polymer dispersed cholesteric liquid crystal(PDChLC)film via a one-step fabrication technique based on photopolymerization of the thiol-acrylatereaction was successfully prepared.Experimental results showed that the pitch of the ChLC plays an important role in determining the electro-optical characteristics of PDChLC film.Both Vth and Vsat continuously increased with the decrease of pitch.Moreover,the CR of the films were to further improve.The Vth and Vsat were higher compared with the system of PDLC.It was mainly due to the shorter the pitch of ChLC,the greater the helical twisting force,therefore the Vth and Vsat of DDCLC films are inversely proportional to the pitch of the ChLC.(3)The effects of different ratios of crosslinking agents?UV curing intensity and curing temperature on the polymer network and the electro-optical properties of PDLC films were investigated.The study found that different ratios of crosslinking agents influence on the mesh size of the polymer network and the sizes of LC domain in PDLC films decreased as well as the increase of the UV curing intensity,while decreased at first and then increased with the gradual increase of the curing temperature. |
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