Experimental design to measure the anchoring energy on substrate surface by using the alternating-current bridge

The anchoring property of the substrate surface of liquid crystal cells plays an important role in display and nondisplay fields. This property directly affects the deformation of liquid crystal molecules to change the phase difference through liquid crystal cells. In this paper, a test method based on the alternating-current bridge is proposed to determine the capacitance of liquid crystal cells and thus measure the anchoring energy of the substrate surface. The anchoring energy can be obtained by comparing the capacitance–voltage curves of twisted nematic liquid crystal cells with different anchoring properties in experimental and theoretical results simulated on the basis of Frank elastic theory. Compared with the other methods to determine the anchoring energy, our proposed method requires a simple treatment of liquid crystal cells and allows easy and high-accuracy measurements, thereby expanding the test ideas on the performance parameters of liquid crystal devices.     

基于液晶动态响应的挠曲电系数测量EI北大核心CSCD

基于自组装的液晶动态响应实验装置,研究了液晶挠曲电效应对强锚泊混合排列向列相(HAN)液晶动态响应过程的影响。实验中HAN液晶盒施加脉宽为250 ms、幅度可调的正负单脉冲电压信号,结果发现:幅度相同的正负脉冲电压信号作用下液晶的动态响应不同,幅度不同的正脉冲或负脉冲电压信号作用下液晶的动态响应也不同。通过幅度不同的正脉冲电压信号(3、4、5、6 V)作用下液晶动态响应实验曲线与考虑挠曲电效应情形下液晶动态响应理论曲线之间的比较,得到了液晶材料E7的挠曲电系数为e11+e33=4.0×10-11C/m,与文献中报道的实验测量值基本一致。     

Influence ofγ-Fe2O3 nanoparticles doping on the image sticking in VAN-LCD

Image sticking in liquid crystal display(LCD)is related to the residual direct current(DC)voltage(RDCV)on the cell and the dynamic response of the liquid crystal materials.According to the capacitance change of the liquid crystal cell under the DC bias,the saturated RDCV(SRDCV)can be obtained.The response time can be obtained by testing the optical dynamic response of the liquid crystal cell,thereby evaluating the image sticking problem.Based on this,the image sticking of vertical aligned nematic(VAN)LCD(VAN-LCD)with different cell thicknesses(3.8μm and 11.5μm)and different concentrations ofγ-Fe2O3 nanoparticles(0.017 wt.%,0.034 wt.%,0.051 wt.%,0.068 wt.%,0.136 wt.%,0.204 wt.%,and 0.272 wt.%)was evaluated,and the effect of nano-doping was analyzed.It is found that the SRDCV and response time decrease firstly and then increase with the increase of the doping concentration ofγ-Fe2O3 nanoparticles in the VAN cell.When the doping concentration is 0.034 wt.%,theγ-Fe2O3 nanoparticles can adsorb most of the free impurity ions in liquid crystal materials,resulting in 70%reduction in the SRDCV,8.11%decrease in the decay time,and 15.49%reduction in the rise time.The results show that the doping ofγ-Fe2O3 nanoparticles can effectively improve the image sticking of VAN-LCD and provide useful guidance for improving the display quality.