Patent ID: 7067180

Claim:
A method of making a liquid crystal alignment layer for bistable nematic liquid-crystal devices, comprising: placing two confinement plates respectively on both sides of a nematic liquid crystal layer, said liquid crystal alignment layer having a strong azimuthal anchoring energy for the liquid crystal layer over at least one of its confinement plates, and having on the same confinement plate a low zenithal anchoring energy so as to allow switching between two states corresponding to bistability; depositing, on a substrate completely free of any previously deposited alignment layer, a polymer or a copolymer or a terpolymer chosen from the polymers or copolymers derived from poly(vinyl chloride-co-vinyl alkyl ether) or from poly(vinyl chloride-co-vinyl aryl ether); stabilizing this polymer coating, the stabilization comprising at least one thermal annealing step making the polymer deposit non soluble in the liquid crystal material and to preserve the anchoring properties of the polymer deposit; and defining an azimuthal orientation of the coating for inducing a strong and controlled azimuthal anchoring of the liquid crystal, the zenithal anchoring having a critical electric field of breaking the anchoring below 10 v/μm, the azimuthal anchoring having an extrapolation length lying in the range of 50 nm to 200 nm, the liquid crystal containing no additive operating on the anchoring properties, wherein all the treatment steps are chosen in order to define a controlled and stable pretilt of the orientation of the nematic liquid crystal lying in the range between 0°and 1°.