A memory-type holographic polymer dispersed liquid crystal (HPDLC) reflective display device

A memory-type colour reflective display device is proposed. Introducing smectic liquid crystal to holographic polymer dispersed liquid crystal (HPDLC) successfully produced a memory function while keeping the advantages of HPDLC. This device is electrically writable and thermally erasable. It was able to maintain the memory state for more than 4 months. The mechanism of the memory function was analysed by comparing three HPDLC devices which were made with three different cyano-biphenyl compounds. The compounds had similar molecular structures but different phase transition temperatures. Small passive matrix devices for three primary colour devices were successfully demonstrated and colour mixing was confirmed to occur on stacking.