Optical switching of nematic liquid crystal by means of photoresponsive polyimides as an alignment layer

Abstract

Photosensitive polyimides (PIs) as an alignment layer induced optical switching of nematic liquid crystal (NLC) on photoirradiation at 366 nm. The orientation of NLC molecule was changed from homogeneous to homeotropic alignment on photoirradiation with a dc electric field as a bias. The optical switching behavior of NLC was largely affected by the chemical structures of PIs.

Photocontrollable Liquid‐Crystalline Actuators

“…Since the transmittance recovers when irradiation is stopped, it is assumed that the optical switching is based on an alignment change between a homogeneous state and a homeotropic state. [ 33 ] Recently, aromatic PIs exposed to LPL with a longer wavelength were reported to show a high effi ciency of photoalignment without any signifi cant change in chemical structures of PIs. [ 34 ] To evaluate the alignment, a PI fi lm formed on a glass substrate was irradiated with LPL at 366 nm, and then an LC cell was fabricated with two pieces of these exposed PI-coated substrates, sandwiching with 5CB between them.…”

“…Ikeda et al studied a dynamic photocontrol of LC alignment, optical switching of nematic LCs using a photo active PI containing a benzophenone moiety as an alignment layer. [ 33 ] An LC cell with a gap of 5 μ m, in which both substrates were coated with rubbed PI fi lms, was fabricated to evaluate the photoresponse of a nematic LC (5CB). The change in transmittance as a function of applied voltage for the LC cell is shown in the left of Figure 3 C, in which the threshold voltage for the electric Freedericksz transition is quite different between the irradiated and unirradiated samples.…”

Photomodulation of liquid crystal orientations for photonic applications

“…27). 169 An LC cell with a gap of 5 mm, in which substrates were coated with PI films and then rubbed, was fabricated to evaluate an optical response of 5CB. Fig.…”

Blends of polypropylene with poly(vinyl butyral)

“…However, this method is accompanied by chemical reactions, resulting in weakening the thermal stability of PIs due to serious degradation of backbone structures. Ikeda et al studied a dynamic photocontrol of LC alignment, optical switching of nematic LCs using a photo­active PI containing a benzophenone moiety as an alignment layer 33. An LC cell with a gap of 5 μm, in which both substrates were coated with rubbed PI films, was fabricated to evaluate the photoresponse of a nematic LC (5CB).…”

“…It was found that photo­irradiation at 366 nm results in an immediate change in transmittance when a bias voltage of 4.5 V is applied across the LC cell. Since the transmittance recovers when irradiation is stopped, it is assumed that the optical switching is based on an alignment change between a homogeneous state and a homeotropic state 33…”