Research On Opto-electric Response Of Liquid Crystal Based On Photo-alignment

Although the rubbing alignment technology is currently widely used,its development is restricted to a certain extent due to its some natural disadvantages,for example,it is inevitable that some dust or electrostatic charges will stray into during the rubbing process,in addition,when the displayed image becomes larger,the rubbing marks will become more obvious,etc.For breaking the through limitations of the rubbing method,scholars have proposed and developed photoalignment technology,which can create high-quality LCD(Liquid crystal display,LCD)without damaging the substrate,avoiding dust and some electrostatic charges.Along with tremendous progress of photo-alignment technology,numerous scholars have proposed an ODLCD(Optically driven liquid crystal display,ODLCD)utilizing photo-alignment technology,different pixels on this new type of display panel can be adjusted by polarized light without consuming any power to display different images.However,due to the longer rewriting time of ODLCD,it is currently limited to laboratory research.Meanwhile,in the past few years,people have put forward higher and higher comprehensive requirements for the performance of LCD,such as low power consumption and better dynamic display performance,which requires LCD to have a lower threshold voltage and response time.Therefore,in order to reduce the writing time of ODLCD and improve the threshold voltage and response time of LCD.In consideration of the photo-alignment,the following contents are studied in this thesis:1.This thesis studied the effect of temperature on the rewriting time of ODLCD,and combined with the current popular new nano-technology,the thesis also studied the effect of NiO nanoparticles doped with alignment material(SD1)on the rewriting time.For the doping of nanoparticles,this thesis designed 11 solutions with different mass ratios,and then used SEM,TEM and AFM to analyze the distribution and morphology of the nanoparticles in the SD1-NiO solution.For the rewriting time of ODLCD,SD1-NiO 1-0.08 is the best,is reduced about 1.5 times compared with the rewriting time of pure SD1 solution.2.In order to study the influence of temperature on ODLCD writing time,this thesis designed five different liquid crystals and in the clearing point under the study of the change of writing time,Finlly,with the rise of temperature,writing time has significantly reduced,especially for N4 liquid crystal,writing time reduced about 24 times.3.This thesis designs experiments based on photo-alignment technology to doping NiO nanoparticles into SD1 solution,and designed different liquid crystal cell gap to observe the impact on the threshold voltage and response time of the liquid crystal cell,and also studied the influences on the response time of different AC voltages in the liquid crystal cell.In the experiment of the influence of NiO nanoparticle doping on the LCD,this thesis found that no matter the gap of the liquid crystal cell or the concentration of nanoparticles,the result is that there is no significant change in the threshold voltage of the liquid crystal cell,because the threshold voltage of the liquid crystal cell is mainly affected by the dielectric anisotropy of the liquid crystal,however,doping the nanoparticles into the alignment agent does not affect the physical properties of the liquid crystal itself.4.In the experiment of researching the elements affecting the response time of the liquid crystal cell,within a limited voltage range,as the AC voltage across the liquid crystal cell increases,the response time is significantly reduced.When nanoparticles are doped into the alignment agent,the results show that the response time decreases significantly with the increase of the concentration of nanoparticles when the concentration of nanoparticles is low.Because when the voltage is turned off,the polarization electric field generated by the nanoparticles will absorb the residual ions in the liquid crystal,thus reducing the response time.And when the gap of the liquid crystal cell is 5um,there is the smallest response time in SD1-NiO 1-0.2,and when the gap of the liquid crystal cell is10 um,there is the smallest response time in SD1-NiO 1-0.3.For different cell gap,there is an optimal doping concentration.Meanwhile,when the gap of the liquid crystal cell decreases,the response time will decrease correspondingly,but this decrease is not proportional to the square of the gap of the liquid crystal cell as in theory,because the gap of the liquid crystal cell is also affected by the pitch of the liquid crystal,so the liquid crystal cell gap can't be reduced blindly.