Drive scheme for cholesteric liquid crystal display device
AssigneeVersatile Technologies Ltd
InventorChristopher John Hughes
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Abstract
A drive scheme for a cholesteric liquid crystal display device comprises supply of a drive signal to the electrode arrangement of a cell comprising a layer of cholesteric liquid crystal material. The drive signal comprises at least one initial pulse that drives the cholesteric liquid crystal material into the homeotropic state; a relaxation period that allows the cholesteric liquid crystal material to relax into the planar state; and a drive sequence during which the root mean square voltage of the drive signal, determined over periods within which the cholesteric liquid crystal does not relax, increases monotonically. The drive sequence reduces the reflectivity of the cholesteric liquid material without any fluctuations.
Claims24
A method of driving a cholesteric liquid crystal display device which comprises at least one cell comprising a layer of cholesteric liquid crystal material and an electrode arrangement capable of applying a drive signal across at least one area of the layer of cholesteric liquid crystal material, the method comprising supplying a drive signal to the electrode arrangement that comprises:
- at least one initial pulse that drives the cholesteric liquid crystal material into the homeotropic state;
- a relaxation period that allows the cholesteric liquid crystal material to relax into the planar state;
- and
- a drive sequence during which the root mean square voltage of the drive signal, determined over periods within which the cholesteric liquid crystal does not relax, increases monotonically and correspondingly reduces the reflectivity of the cholesteric liquid material.
A cholesteric liquid crystal display device comprising:
- at least one cell comprising a layer of cholesteric liquid crystal material and an electrode arrangement capable of applying a drive signal across at least one area of the layer of cholesteric liquid crystal material;
- and
- a drive circuit arranged to supply a drive signal to the electrode arrangement that comprises:
- at least one initial pulse configured to drive the cholesteric liquid crystal material into the homeotropic state;
- a relaxation period configured to allow the cholesteric liquid crystal material to relax into the planar state;
- and
- a drive sequence during which the root mean square voltage of the drive signal, determined over a period within which the cholesteric liquid crystal does not relax, increases monotonically and configured to correspondingly reduce the reflectivity of the cholesteric liquid material.
Dependencies are inferred from the claim text.