New principle of optical data recording based on reversible transition "selective reflection-absorbance" in photochromic cholesteric copolymers

A new principle of information storage based on a realization of the revers ible transition <<selective reflection-absorbance>> in photochromic liquid crystalline (LC) copolymers was suggested. For this purpose a new family of triple copolymers were synthesized by copolymerization of acrylic monomers , containing nematogenic (phenylbenzoate), chiral (cholesterol), and photoc hromic (spiropyran) fragments. Phase behaviour and optical properties of co polymers were studied. Isomerization of spiropyran groups and formation of merocyanine form under UV-irradiation (337 nm) of the polymer films was obs erved. It should be noted that the maximum of the absorbance of polymer fil ms coincides with maximum of selective light reflection. As a result the di sappearance of the selective light reflection in the irradiated regions of the films occurs. Scheme of the optical data recording and reading of infor mation recorded on planarly oriented films of such copolymers was proposed.