Laboratory for Information and Functions of Materials (Usami Lab)
（Laboratory for Information and Functions of Materials）
1. Research topics
a. Control of molecular orientation of liquid crystal molecules by using
photo-aligned polyimide films [1,3,5,6]
Photo-induced alignment of liquid crystal molecules is a promisingalternative to the conventional rubbing technique, because
photo-alignment is mechanical-contact-free and has high reproducibility
and uniformity over a large-area substrate. Among various
photo-alignment methods, we are focusing on a method using films ofpolyimide containing azobenzene in the backbone structure (Azo-PI). The
Azo-PI films are thermally, chemically and optically stable. In addition, wedemonstrated that the in-plane anisotropy much larger than that induced
by rubbing can be optically induced, and also that the azimuthal anchoringenergy coefficient is comparable to or larger than that of conventionalrubbed polyimide alignment layers.
b. Liquid crystals alignment on perfluoropolymer films [4]In liquid crystal displays (LCDs), weak anchoring of the liquid crystal(LC) molecules at the interface with the alignment layer can in principle
lead to lower operating voltages and improved steepness of theelectro-optic response [G. P. Bryan-Brown et al., Nature 399, 338 (1999)].
It was reported that Langmuir-Blodgett films of perfluoropolyether had aweak surface anchoring for bend deformation, which was in the order of
10-5 J/m2 for 4-n-pentyl-4'-cyanobiphenyl[J. M. Russell-Tanner et al., J.
Chem. Phys. 126, 244706 (2007)]. The perfluoropolyether film has highthermally and chemically resistant, high gas permeability, and low toxicity.
Up to now, we succeeded in inducing a uniform LC alignment by using
Fluorocur films exposed to linearly polarized ultraviolet light.
c. Optically isotropic chiral domains in bent-core liquid crystals [2]Bent core liquid crystals are a class of materials that are interesting
both for their fundamental theoretical study and for the applications that
may be exhibited via their unique phases. Recently, the optically isotropic
phases that have been observed in some bent-core materials have received

much attention, both with respect to fundamental structural studies andbecause of new modes of optical switching in devices. In both cases,chiral domains can be observed in the optically isotropic phase, with equaldistributions of domains with opposite chirality. Recently, we found thatlarge optically isotropic chiral domains can be generated in the opticallyisotropic phase of C5-Ph-ODBP-Ph-OC12 by applying an electric field.

2. Featured publications
1. K. Sakamoto, K. Usami, and K. Miki, “Photoalignment efficiency enhancement ofpolyimide alignment layers by alkyl-amine vapor treatment,” Appl. Phys.
Express 7, 081701 (2014).
2. M. Nagaraj, K. Usami, Z. Zhang, V. Görtz, J. W. Goodby, and H. F. Gleeson,“Unusual electric-field-induced transformations in the dark conglomerate
phase of a bent-core liquid crystal”, Liq. Cryst. 41, 800-811 (2014).
3. K. Usami and K. Sakamoto, “Photo-aligned blend films ofazobenzene-containing polyimides with and without side-chains for inducing
inclined alignment of liquid crystal molecules”, J. Appl. Phys. 110, 043522(2011).
4. K. Usami, A. Sugimura, and E. T. Samulski, “Uniform alignment of liquid crystalsinduced by perfluoropolyether film exposed to linearly polarized ultravioletlight”, Mol. Cryst. Liq. Cryst. 516, 38-44 (2010).
5. K. Usami, K. Sakamoto, J. Yokota, Y. Uehara, and S. Ushioda, “Pretilt angle
control of liquid crystal molecules by photoaligned films ofazobenzene-containing polyimide with a different content of side-chain”, J.
Appl. Phys. 104, 113528 (2008).
6. K. Usami, K. Sakamoto, Y. Uehara, and S. Ushioda, “Transfer of the in-plane
molecular orientation of polyimide film surface to liquid crystal monolayer”,
Appl. Phys. Lett. 86 (21), 211906 (2005).

3. Corporate and other affiliates
a. National Institute for Materials Science (NIMS), Chisso Petrochemical
Corporation
Joint research related to polyimide photoalignment films undertaken by
NIMS principal researcher Kenji Sakamoto and Chisso PetrochemicalCorporation