Research On Liquid Crystal Display Film Of Low Energy Consumption And High Contrast

Liquid crystals（LC）play an important role in the field of electro-optical displays for their unique optical and dielectric anisotropy as well as mobility,where liquid crystal composites have become an important material.Lower drive voltage and higher contrast ratio are valuable parameters for their performance of low energy consumption and excellent display characteristics.Polymer dispersed liquid crystals（PDLC）occupy an important position in the flexible display and smart window materials by combining the electric field response properties of liquid crystals with the mechanical properties and flexibility of polymers.Liquid crystal physical gels（LCPG）can significantly reduce the power consumption and contrast of electro-optical display films using trace amounts of gel molecules which is an excellent material for a complete physical formation process.In this paper,we designed a double-layer PDLC film that can be displayed in steps,and the simple preparation process reduces the energy consumption of the film device,as well as obtains a contrast similar to that of single-layer PDLC,with better performance results;in addition,we formulated a series of LCPG solutions and successfully prepared a new type of trans-LCPG film with power-on scattering and power-off transparency,which greatly reduces the energy consumption of the film with the off state transparent film.Moreover,the prepared films have lower driving voltage,higher contrast,and faster response time.Details of the research are as follows.（1）A series of monolayer PDLC films with low driving voltages were prepared and characterized,and the connection between film micromorphology and electro-optical properties was delicately elaborated.Two single-layer PDLC films were combined with a distinct value difference between threshold voltage(V_th)and saturation voltage(V_sat)with_sat<_th,whilst double-layer PDLC films were prepared using a coating and rolling process followed by the polymerization-induced phase separation（PIPS）method.The effects of double-layer PDLC films prepared from the same polymer substrate and different polymer substrates on driving voltage and contrast were investigated,and the stepwise driving phenomena were mutually verified by physical and simulation methods.The results show that the double-layer PDLC films obtained from the combination of different polymer substrates have better integrated electro-optical properties and layered display effects,which is an important method to prepare low-power and high-contrast double-layer films.（2）A series of LCPG material formulations were designed to investigate the connection between liquid crystal anisotropy-isotropy transition temperature(T_IA)and sol-gel transition temperature(T_SG)as well as the effect on phase transition temperature after gel doping with cholesteric phase liquid crystal.The trans-LCPG films were prepared by using oriented liquid crystal cartridges for the configured LCPG solutions separately,then the effects of chiral compound S811 and a trace amount of gel DMDBS on the transmittance in the visible region,driving voltage,contrast,and response time of trans-LCPG films were investigated,so that the best overall performance film was screened.Furthermore,the images of the optimal film under polarized light microscopy（POM）were compared with the images of pure cholesteric phase liquid crystal,observing the wide distribution of gel molecules,and the cycle duration was also monitored and tested.Finally,an excellent trans-LCPG film with a driving voltage less than the human safety voltage and a response time lower than the human eye response time was obtained.