Effects of electrode structure and dielectric anisotropy on the performance of VA-FFS LC mode

Vertically-Aligned Fringe-Field Switching (VA-FFS) liquid crystal (LC) mode is known for its intrinsic submillisecond fast response time due to existence of self-imposed boundaries of virtual walls. In this paper, we investigate the effects of electrode structure and LC dielectric anisotropy. The performance of VA-FFS with conventional 2D and 3D electrode designs are compared. By using the 3D electrode design, higher transmission and faster response time are found possible as a result of having less dark states and at the same time having more virtual walls surrounding a 3D pixel. In the second part, we investigate the difference between VA-FFS LC mode employing LC materials with positive and negative dielectric anisotropy, while keeping all other factors the same. We found that, in general, positive LC materials can provide faster response time whereas negative LC materials can provide higher transmission. In the case of 2D design, however, negative LC is found to have rather unexpected slow response times due to i) existence of a 2-step switching process and ii) disappearance of virtual wall, which have never been reported or published before for VA-FFS. In this paper, we will show that, by using a 3D design, both of these problems for negative LC can be improved such that 3D design can help maintain the stability of virtual walls and also help bring the response time of negative LC closer to that of positive LC. VA-FFS LC has been actively researched for VR/AR application in recent years.