液晶材料电学特性随温度变化研究

Electrical properties of liquid crystal materials with temperature

温度变化会对液晶材料的电学特性产生影响。为了深入探究低温下液晶材料的电学特性,首先,液晶盒厚度和取向层厚度分别由紫外可见分光光度计和表面轮廓仪测量得到;然后,利用精密热台以及基于热电制冷工作原理自制的制冷装置控制液晶盒的温度,使用校准后的精密LCR表分别测得低温和常温下液晶盒电容-电压(C-U)特性曲线,由液晶盒电容模型得到液晶层C-U特性曲线,基于该曲线与双盒模型,得到了温度对4种液晶介电各向异性、弹性常数的影响。实验结果表明随着温度的升高,正性液晶材料的介电各向异性从10.0增大至21.0,弹性常数k_(11)从17.0 pN减小至7.0 pN,k_(33)从31.0p N减小至16.0 pN;负性液晶材料的介电各向异性从-8.5增大至-3.0,k_(11)从21.0 pN减小至11.0 pN,k_(33)从31.0 pN减小至13.0 pN。即随着温度的升高,正性液晶材料的介电各向异性和弹性常数k_(11)、k_(33)均不断减小;负性液晶材料的介电各向异性不断增大,k_(11)、k_(33)呈现减小趋势。该结论对探究低温下提升液晶显示性能的方法有着重要意义。

The change of temperature can affect the electrical properties of liquid crystal(LC)materials.In order to further explore the electrical properties of LC materials at low temperature,firstly,the thicknesses of the LC cells and the polymide(PI)alignment layers were measured by UV spectrophotometer and surface profiler respectively.Then,a precision hot stage and a self-made refrigeration device based on the working principle of thermoelectric refrigeration were used to control the temperature of the LC cell,and the precision LCR meter which was calibrated was applied to measure the capacitance-voltage(C-U)curve of LC cell at low and normal temperatures.The C-U curve of LC layer could be obtained by using the capacitance model of LC cell,and based on this curve and dual-cell model,the effects of temperature on dielectric anisotropy and elastic constant of four kinds of LCs were obtained.The experimental results show that the dielectric anisotropy of the LC with positive dielectric anisotropy increases from 10.0 to 20.0,and the elastic constant k_(11) decreases from 17.0 pN to 7.0 pN,and k_(33) decreases from 31.0 pN to 15.0 pN.The dielectric anisotropy of the LC with negative dielectric anisotropy increases from-8.5 to-3.0,decreases from 21.0 pN to 11.0 pN for k_(11),and from 31.0 pN to 12.0 pN for k_(33).The dielectric anisotropy and elastic constant k_(11) and k_(33) of the LC with positive dielectric anisotropy decrease with the increase of the temperature,and increase and decrease respectively with increasing temperature for the LC with negative dielectric anisotropy.This conclusion is of great significance for exploring the methods to improve the performance of liquid crystal display at low temperature.