Mizuho Kondo

Copolymer films of photoalignable liquid crystalline (LC) copolymethacrylates comprised of a phenyl benzoate mesogen connected with N-benzylideneaniline end moiety (NBA2) and benzoic acid (BA) side groups exhibit a photoinduced reorientation behavior. Significant thermally stimulated molecular reorientation attains a dichroism (D) greater than 0.7 for all copolymer films and a birefringence of 0.113–0.181. In situ thermal hydrolysis of the oriented NBA2 groups decreases the birefringence to 0.111–0.128. However, the oriented structures of the film are maintained, demonstrating a photo-durability, even though the NBA2 side groups photo-react. The hydrolyzed oriented films show higher photo-durability without changing their optical properties.

Photoinduced reorientation of composite films of liquid crystalline polymethacrylate comprised of benzoic acid (BA) side groups with different length alkylene spacer (PnBAM n = 2, 6, 10) and N-benzylideneaniline carboxylic acid (NBA) is investigated using linearly polarized (LP) 365 nm light. Significant thermally stimulated in-plane molecular orientation is attained when P6BAM (n = 6) is used, but higher amount of NBA is required for the in-plane reorientation of P2BAM (n = 2) films and out-of-plane motion of the BA side groups is observed for P10BAM (n = 10) films.

Diblock and random copolymers are synthesized from a methacrylate with benzoic acid (BA) side groups and a n-butyl methacrylate, and the photoinduced reorientation of thin films doped with a N-benzylideneaniline carboxylic acid (NBA), which governs the H-bond with BA, is investigated using linearly polarized (LP) 365 and 313 nm light. A sufficient thermally stimulated photoinduced orientation of the BA side groups and simultaneous sublimation of NBA are attained for the diblock copolymer films, whereas a thermal treatment results in the random orientation of the random copolymers. Furthermore, surface relief (SR) formation of the film is explored when the NBA-doped films are exposed to LP light using a photomask. The liquid crystalline characteristics, thermal properties, axis-selective photoisomerization, and the photo-cross-linking of the film play important roles in the molecular reorientation and SR formations.

Photoalignment of low-molecular-liquid crystalline (LC) cell is explored without surface treatment of the substrates. A linearly polarized (LP) light exposure to a LC cell containing nematic LCs and a small amount of photoresponsive material generates homogenous LC orientation of the cell. Material design, mixture ratio and exposure condition are investigated.