Coatable Compensator for Flexible Display: Single-Layered Negative Dispersion Retarder Fabricated by Coating, Self-Assembling, and Polymerizing Host–Guest Reactive Mesogens

• Published in: ACS applied materials & interfaces 2019-05, Vol.11 (19), p.17766-17773
• Main Authors: Choi, Yu-Jin, Yoon, Won-Jin, Bang, Geukcheon, Jeong, Jinyoung, Lee, Ji-Hoon, Kim, Namil, Jeong, Kwang-Un
• Format: Article
• Language: English
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.9b02571

Antireflective films for flexible display devices should be made by a coating process rather than a stretching process. Additionally, the compensator, which is the core of the antireflective film, must exhibit a wavelength-independent phase retardation in the visible-light region to act as an ideal retarder. To satisfy all of these requirements, we intend to make a single-layered negative dispersion retarder (SNDR) with a single coating process followed by polymer stabilization. To achieve this goal, X-shaped reactive mesogen (X2RM) is newly synthesized as a guest RM and mixed into a host RM that exhibits a smectic A mesophase. Based on the thermal, spectroscopic, microscopic, and scattering analyses combined with computer simulation, the content of X2RM in the HCM026 molecule is optimized to be 40 wt %. The SNDR thin film is fabricated by coating the optimized H–G mixture on the rubbed alignment substrate and subsequent heat treatment. The trans-to-cis photoisomerization of imine bond can help X2RM to be located in the smectic interlayer of the HCM026. The molecular long axis of HCM026 is parallel to the rubbing direction of the alignment layer and the conjugated benzene rings of X2RM aligned perpendicular to the molecular long axis of smectic RM, which is the ideal molecular arrangement of negative dispersion retarder. Additionally, polarized UV polymerization improves the mechanical and chemical stability as well as the molecular orientation of SNDR.