PHOTOCHEMICAL SWITCHING OF POLARIZATION IN FERROELECTRIC LIQUID-CRYSTAL FILMS

LIQUID crystals have been used extensively as active media in display devices such as full-colour television screens. These devices are generally based on changes in the arrangement of the liquid-crystal molecules induced by electric fields, which change their optical properties1. Ferroelectric liquid crystals2,3 exhibit spontaneous polarization and therefore show a faster response to changes in the applied field. Switching of this field causes a reversal in the direction of polarization2-5. Here we report polarization switching in ferroelectric liquid crystals driven by a photochemical process. The liquid-crystal films are doped with a photochromic compound which undergoes trans-cis isomerization on irradiation. Photoisomerization induces a change in the switching potential of the host liquid-crystal film, and thereby causes switching at the irradiated sites. The process is fast, stable, reversible and repeatable, and should be exploitable in device applications.