Bistable nematic liquid crystal device

一个双稳向列相液晶装置盒在至少一个盒壁上提供了一个表面准直光栅和在另一个盒壁上提供了表面处理。这样的处理可为垂向准直或具有或不具有准直方向的平面准直，以及零或非零预倾角。在单光栅上的表面外廓是不对称的，在其两个容许的准直排列中其沟槽的高宽比选择为在向列相材料中给出大致相等能量。单光栅可通过光刻过程或通过塑料材料模压而形成。通过直流脉冲与材料中可变电系数的耦合，或通过两个频率可寻址方案和一个适当的两个频率材料的使用，液晶盒被切换。液晶盒每边的偏振器在两个切换状态之间被分辨。盒壁可为刚性的或柔性的，并涂覆有电极结构，如以行和列形式给出在液晶盒上的可寻址象素的x，y矩阵。 A bistable nematic liquid crystal device cell is provided with a surface alignment grating on at least one cell wall and a surface treatment on the other wall. Such treatment may be a homeotropic alignment or a planar alignment with or without an alignment direction, and zero or a non zero pretilt. The surface profile on the monograting is asymmetric with its groove height to width selected to give approximately equal energy within the nematic material in its two allowed alignment arrangements. The monograting may be formed by a photolithographic process or by embossing of a plastics material. The cell is switched by dc pulses coupling to a flexoelectric coefficient in the material, or by use of a two frequency addressing scheme and a suitable two frequency material. Polarisers either side of the cell distinguish between the two switched states. The cell walls may be rigid or flexible, and are coated with electrode structures, e.g. in row and column format giving an x,y matrix of addressable pixels on the cell.