Technologies towards patterned optical foils applied to transflective LCDs

Abstract

Abstract— For better front‐of‐screen performance for transflective LCDs, a technology with extra free optimization parameters for the optical stack is needed. Thin wet coatable retarders which enable adjustment of the optical activity on the (sub)pixel level have been developed. Isotropic domains have been created in nematic retardation films by thermal patterning or photopatterning. Employing such a patterned retarder in a transflective LCD leads to an LCD that is lighter and thinner with good reflectivity, high transmission, and low chromaticity at all gray levels and wide viewing angles. The patterned thin‐film technology has been proven to be versatile and applicable in various LCD designs.

Patterned retarders prepared by photoisomerization and photopolymerization of liquid crystalline films

“…Therefore, technologies available for creating alternating retardation values in micrometer thin retardation films made according to the LC-network technology include director patterning (h) [4,8], thickness (d) variations [8,9] or variations in birefringence (Dn) [10]. For the fabrication of patterned thin film retarders applied in the transflective LCD design given in figure 1, birefringence patterning is preferred to director and thickness patterning because the optical characteristics of an isotropic domain are viewing angleindependent, and surface flatness is required for the assembly and optimal front-of-screen performance of the final LCD.…”

“…Dn50, and the film becomes optically inactive. Combination of this phase transition with in situ photopolymerization results in a patterned thin film retarder [10,11]. This is achieved by conducting in succession a mask exposure to crosslink the film locally in its nematic state and a flood exposure at a temperature exceeding the nematic-to-isotropic (N-I) transition temperature of the liquid crystalline monomers to fix the remaining isotropic areas.…”

O films with adjustable tilt of optical axis for LCD compensation

“…13,14 Furthermore, it can be also extended to photoalignment by using photosensitive p-PI and/or h-PI materials as it was recently realized for conventional LC 15 . In this way, patterned O films can be easily obtained, which, compared with known solutions, 16,17 open new compensation possibilities for recently developed LCD modes (e.g., transflective and stereoscopic LCDs).…”

Patterned retarder films using reactive mesogen technology

“…For example, after the mask aligner step, the resulting films produced could be uneven due to diffusion of the non-polymerised RM 15 . A trade-off between well polymerised films and good edge resolution was also typically observed.…”