Research On One-dimensional Model Of Blue Phase Liquid Crystal Display

Blue phase liquid crystal display(BPLCD)is regarded as the next-generation liquid crystal display technology because of its fast response speed,wide viewing angle and simple fabrication processes.However,the high operating voltage,hysteresis effect and residual birefringence cannot be solved in recently ten years.As people study the blue phase liquid crystal(BPLC)and BPLCD,found the lattice model to describe the molecules arrangement,which can calculate Bragg reflection and optical rotatory.The extended Kerr equation is obtained from the experimental electrical-birefringence curves,and can calculate the transmittance and viewing angle of BPLCD.However,no theory or equation can describe or calculate the dynamic response and hysteresis effect.In this thesis,the optical threshold and saturation voltages of BPLCD is firstly researched using one-dimensional model in the first part,the product of the saturation birefringence of blue phase liquid crystal(BPLC)and liquid crystal layer's thickness is optimized for low operating voltage BPLCD.The driven electric field strength in the existing various BPLCDs is studied in detail,the optimized BPLCD configuration is obtained by compared with the condition for eliminating the hysteresis effect.Secondly,considered the dielectric constants of the materials in BPLCD,the influence of the dielectric constants on the distribution of electric potential is researched by using one-dimensional model,the electric field strength in low dielectric constant material is more larger than that in high dielectric constant material,as a result,the polymer and chiral dopant with high dielectric constant can obviously reduce the operating voltage of BPLCD.In the third part,considered the similar configuration and optical profiles of cholesteric and BPLC,the like cholesteric liquid crystal one-dimensional model is founded,simulating the Bragg reflection of blue phase liquid crystal.Also,the surface dynamic equations of blue phase liquid crystal and the dynamic equation of polymer net is founded by considering the optical properties of polymer stabilized blue phase liquid crystal display(PS-BPLCD),and the effective elastic parameter of BPLC,the effect of the weak anchoring between polymer net surface and liquid crystal,the effect of dynamic response of the surface and bulk of polymer on the response of BPLC,were researched.Through simulated electric-optical curve to fit the experimental results,the effective elastic parameter androtational viscosity of BPLC were obtained,the effective rotational viscosity of polymer surface has large different in the turn-on and turn-off processes,and the rotational viscosity of polymer can affect the hysteresis.The equations of response times of BPLCD were obtained and the cause of hysteresis effect was also obtained.Moreover,one-dimensional model was used to study the rotatory characteristic of BPLC,the specific circle polarizers have to be needed to eliminate the Bragg reflection of BPLC and the transmission induced by optical rotatory for obtaining the high contrast ratio when the Bragg reflection wavelength is designed in the visible light range.The results show that the high dielectric constant polymer and chiral material can reduce the operating voltage of BPLCD,the chose of polymer material has important effect on the hysteresis effect,and the increasing pitch of BPLC with the suitable polarizers can increase the Kerr constant of BPLC.The results are expected to offer the more effective and efficient methods for improving the properties of BPLCD.