Liquid crystal alignment

A liquid crystal device comprising a first cell wall and a second cell wall enclosing a layer of liquid crystal material;

• electrodes for applying an electric field across at least some of the liquid crystal material;
• and
• a surface alignment structure on a region of a substantially planar inner surface of at least the first cell wall, the alignment structure inducing the liquid crystal material in said region to adopt a desired alignment in an azimuthal plane,
• wherein said surface alignment structure comprises a two dimensional array of upstanding posts formed from a photoresist or a plastics material and which are shaped and oriented to produce the desired alignment;
• each post extending substantially orthogonally to said planar inner surface and having a free end surface which is substantially planar and substantially parallel to said planar inner surface, the free end surface having a shape which has no plane of symmetry orthogonal to said azimuthal plane and to said planar inner surface.

A liquid crystal device comprising a first cell wall and a second cell wall enclosing a layer of liquid crystal material;

• electrodes for applying an electric field across at least some of the liquid crystal material;
• and
• a surface alignment structure on a region of a substantially planar inner surface of at least the first cell wall, the alignment structure inducing the liquid crystal material in said region to adopt a desired alignment in an azimuthal plane,
• wherein said surface alignment structure comprises a two dimensional array of blind holes formed in a layer of a photoresist or a plastics material and which are shaped and oriented to produce the desired alignment;
• each hole extending substantially orthogonally to said planar inner surface and having a blinding surface which is substantially planar and substantially parallel to said planar inner surface, said blinding surface and having a shape which has no plane of symmetry orthogonal to said azimuthal plane and to said planar inner surface.

A liquid crystal device comprising a first cell wall and a second cell wall enclosing a layer of liquid crystal material;

• electrodes for applying an electric field across at least some of the liquid crystal material;
• and
• a surface alignment structure on a region of a substantially planar inner surface of at least the first cell wall, the alignment structure inducing the liquid crystal material in said region to adopt a desired alignment in an azimuthal plane,
• wherein said surface alignment structure comprises a two dimensional array of microstructures which are shaped and oriented to produce the desired alignment;
• each microstructure being substantially cylindrical or truncated conical and extending to a distance in the range about 150 nm to about 5 μm normal to said planar inner surface, said cylinder or cone having a base shape which has no plane of symmetry orthogonal to said azimuthal plane and to said planar inner surface;
• but not including any device in which the surface alignment structure comprises a sinusoidal bigrating.

A bistable liquid crystal device comprising a first cell wall and a second cell wall enclosing a layer of liquid crystal material;

• electrodes for applying an electric field across at least some of the liquid crystal material;
• and
• a surface alignment structure on a region of a substantially planar inner surface of at least the first cell wall, the surface alignment structure providing an alignment to the liquid crystal molecules,
• wherein said surface alignment structure comprises a two dimensional array of microstructures which are shaped and oriented to induce the liquid crystal director adjacent said microstructures to adopt two different tilt angles in the same azimuthal plane;
• each microstructure extending to a distance in the range about 150 nm to about 5 μm normal to said planar inner surface and having a cross sectional shape which has no plane of symmetry orthogonal to said azimuthal plane and to said planar inner surface;
• said microstructures not being treated with or formed from a material which induces local homeotropic alignment of said liquid crystal material;
• the arrangement being such that two stable liquid crystal molecular configurations can exist after suitable electrical signals have been applied to said electrodes.