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Display without losing memory : Nematic bistables for display devices.


Philippe Martinot-Lagarde (May-June 2000)

Liquid crystals fundamental studies, developed in the Laboratoire de physique des solides d’Orsay, have been at the origin in of the creation of a SME company near Paris, Nemoptic. It will operate the patents that have been filed by this laboratory concerning the bistable nematic materials, in order to realise display devices with a low energy consumption and a large surface, using an original technology that is less expensive than the present flat screens technologies.

Applying an electrical field causes the states (a) or (b) to distort in (c), where the liquid crystal is aligned along the field within the whole cell, including at the interfaces, due to the break of anchoring at the walls. If the field is abruptly decreased, the interface molecules rapidly return to their usual anchoring, inducing hydrodynamic currents that make the configuration (c) rapidly switch to the so-called "twisted" (b) state. On the other hand if the field is slowly decreased, hydrodynamic effects are absent so that the system enters the so-called "parallel" (a) configuration. As a consequence the profile of field decrease controls the passing from an anchoring state to another, and thus the time of display or erasing.

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