Multi-Domain Alignment of Liquid Crystal Using a Stamp of Anisotropic Morphology Fabricated by a Directional Polymerization of Reactive Mesogen

Abstract

We proposed a simple method to control liquid crystal (LC) alignments by a replication method of directional polymerization of reactive mesogen (RM). The RM polymer structures with nano-grooves were prepared by ultraviolet exposure to the RM mixed alignment layer in a LC cell and transferred to a polyimide by stamping method, which directly replicated the LC alignments of the LC cell. The transferred polyimide layer generated the stable multi-domain alignments of the LC without any aligning processes nor any electrode patterns.

One Methylene Group in the Side Chain Can Alter by 90 Degrees the Orientation of a Main-Chain Liquid Crystal on a Unidirectional Substrate

“…This method has also several disadvantages such as sensitivity to scratches on the alignment surface, dust generation from cloths or synthetic fibers, and static electricity resulting in display defects. 22,23 A promising way to prepare highly oriented and molecularly smooth semicrystalline polymer layers on rubbed polytetrafluoroethylene (PTFE) was proposed by Wittmann and Smith. 24 Rigidity, stability, and high melting temperature of PTFE could potentially make this method efficient for optical LC films, including displays.…”

“…However, despite intense research efforts, the detailed mechanism of the LC alignment by polymer buffing is still a matter of debate. − The most probable explanation for the planar LC alignment is the existence of microgrooves created while buffing the polymer surface. ,,,, In other words, orientation of the LC phases occurs via graphoepitaxy. This method has also several disadvantages such as sensitivity to scratches on the alignment surface, dust generation from cloths or synthetic fibers, and static electricity resulting in display defects. , …”

“…Taking into account that there is a high demand for new alternative methods of LC layer alignment for organic electronics and, in particular, for the LCD technology, , the reported alternating alignment mechanism of the model columnar LCs could be of potential interest to fabricate multidomain LCD that have superior properties with respect to the traditional twisted-nematic (TN) LCDs. Various approaches have been reported to achieve a multidomain alignment (MDA) including polymerization of reactive mesogen or inkjet-printed microprotrusions, however, they are rather complex and challenging for the upscaling. Figure S2 shows a hypothetical example of a LC-based display with three pixels and RGB filters where each color pixel contains 2 subpixels with two mutually orthogonal LC orientations.…”