Patent WO-2013165277-A2 (WO)
Title: Method for producing an oriented liquid crystal layer
Inventor: BELYAEV VIKTOR VASILIEVICH
Filed: 2013-04-29
Abstract: The present invention relates to the field of instrumentation and display and information technology containing liquid crystals. In the claimed method for producing an oriented liquid crystal layer, which includes applying a metal oxide layer to the surface of a substrate, forming a porous structure in said layer and subsequently applying a layer of liquid crystal, the porous structure of the metal oxide on the substrate is modified, prior to the application of the liquid crystal layer, by means of the application of an isotropic liquid solution of a dichroic substance to the surface of the metal oxide layer, then the solvent is evaporated from the aforesaid liquid solution so that a layer of solid state dichroic substance is formed on the surface and in the body of the porous metal oxide layer, this porous layer is heat treated, then the resultant layer is treated with a solvent which does not contain a dichroic substance until a monomolecular dichroic substance layer is produced on the surface of and inside the pores of the metal oxide, whereupon the dichroic substance layer is heated to evaporate the remaining solvent from the porous structure and the resultant monomolecular dichroic substance layer is irradiated with activating optical radiation which is absorbed by the dichroic substance to produce a given orientational order of anisotropic molecules in the monomolecular dichroic substance layer, the substrate with the irradiated monomolecular dichroic substance layer is additionally heated and then liquid crystal material is applied to the resultant surface of the monomolecular dichroic substance layer to form an oriented liquid crystal layer. The dichroic substance used in the present method is in the form of substances which anisotropically absorb light, manifesting the effect of photoinduced optical anisotropy under the influence of the radiation which they absorb. Such dichroic substances which anisotropically absorb light are used in the from of photoanisotropic substances belonging to the class of water-soluble acid-mordant azo or aniline dyes containing СООН, ОН, NH, Cl, Br groups, i.e. groups which are capable of forming specific quasi-chemical bonds, e.g. hydrogen bonds, with the molecules of metal oxides. The photoanisotropic substance used can be, for example, a photochemically stable bis-azo dye, more specifically a sodium salt of 4,4'-bis(4-hydroxy-3-carboxy-phenylazo) benzidine-2,2'-disulphonic acid. The metal oxides with a porous structure are metal oxides selected from Al 2 O 3 , ln 2 O 3 , Sn 2 O 3 , SiO, SiO 2 . The activating optical radiation absorbed by the molecules of the dichroic substances is polarized. In another embodiment, the activating optical radiation absorbed by the molecules of the dichroic substances is non-polarized but is directional. The orientational order of the anisotropic molecules in the monomolecular dichroic substance layer corresponds to the direction of the polarization vector or to the direction of propagation of the activating radiation. In a claimed embodiment, the liquid crystal layer is oriented according to the direction of the orientational order of the molecules in the monomolecular dichroic substance layer. The molecules of the liquid crystal layer are oriented in such a way as to produce a planar orientation which is uniform across the surface and has a given optical axis direction. In another embodiment, the molecules of the liquid crystal layer are oriented in such a way as to produce a two-dimensional visual orientational distribution of the optical axis across the surface.