Tuning Of Polymer-wall Surface Components And Its Effect On The Optoelectronic Performance Of Liquid Crystal Devices With Polymer Walls

Flexible liquid crystal displays(LCDs)are technologically important because they are thin,light weight,and bendable if plastic substrates are used.However,plastic substrates cannot provide a sufficiently firm mechanical support for sustained inter-molecular alignment,which creates many problems for flexible LCDs.One problem is that the thickness changes if the liquid crystal(LC)layer sits on a curved substrate.The inhomogeneous distribution of LC layer thickness leads to poor image display quality because the retardation of light though the LC layer depends not only on the refractive index but also the thickness of the LC layer.The construction of adhesive spacers structure inside LC layer can help sustain the thickness of the LC layer.Among such techniques,polymer-wall structure in the LC layer is particularly useful in plastic substrates for improving the mechanical properties of a wide range of displays.This is done by providing a pressure-resistant,self-adhering,and self-sustaining film.Various methods of forming polymer walls have been reported,but few studies on the surface composition of polymer walls can be found.A very important factor affecting the optoelectronic properties of polymer wall liquid crystal devices is the anchoring force of the polymer to which the liquid crystal is subjected.There is not only the influence of the polymer morphology,but also the material itself.Therefore,this paper explores the effect of surface energy,monomer and liquid crystal compatibility on the surface composition of polymer walls,as well as the modulation of surface composition by polymerization light intensity,and finally the application of this law to polymer wall liquid crystal devices to improve the optoelectronic properties.In order to facilitate the investigation of surface composition,polymer films layered with liquid crystals were prepared by surface initiation in this paper,and the samples were etched by reactive ion etching(RIE)into a stepped shape so that the component changes at different depths could be analyzed.And the samples were prepared under different light intensities and the composition of the surface components was probed.Surface composition analysis by Attenuated Total Reflection(ATR)and X-ray photoelectron spectrometer(XPS)revealed that during the polymerization process,low surface energy components were thermodynamically driven to aggregate at the liquid crystal-polymer interface.During the polymerization process,as the UV intensity decreased,more low surface energy components PHFMA aggregated on the polymer wall surface.The low surface energy components are 8.6%more at low light intensities than at high light intensities.This surface bias effect not only reduces the anchoring energy of the polymer wall,but also reduces the threshold voltage and response time of the polymer wall liquid crystal device.As for the compatibility,it was found experimentally that the component PTFEMA,which is more compatible with liquid crystals,is enriched on the surface and decreases with increasing depth.Compared with high light intensity,the surface of the sample prepared at low light intensity contains more PTFEMA components,10.6%more.Although the surface energies of PTFEMA and PAAEM are similar,differing by only0.6 m J/m~2,the prepared polymer wall liquid crystal devices have lower threshold voltage,saturation voltage,and response time due to the slightly lower surface energy of PTFEMA and the fact that it will be more easily enriched at the polymer wall-liquid crystal interface at low polymerization light intensities.The final PET-based flexible polymer wall liquid crystal devices were prepared to achieve switching of transmittance during bending with no change in display.These provide new improvements in the optoelectronic properties of polymer wall liquid crystal devices for flexible displays.