Thales

Nemoptic

France Brevets

Cécile Joubert

Claude Bricot

Brigitte Loiseaux

Philippe Robin

Daniel Stoenescu

Alexandre Carton

Patrice Davi

Terry J Scheffer

Laurent Bignolles

Bertrand Morbieu

The application relates to a single-polarizer reflective bistable twisted nematic (BTN) liquid crystal display device comprising a liquid crystal layer of thickness d, birefringence &#x394;n and retardation &#x394;nd, said liquid crystal layer being situated between two substrates and between a polarizer and a reflector, said liquid crystal layer in the absence of an applied electric field having two stable uniformly twisted textures, the twists of the two stable textures differing by an angle being equal mainly to 180&#xb0;, and at least one compensation layer positioned between said polarizer and said reflector, said compensation layer being composed of at least one birefringent film, said birefringent film having an optical anisotropy defined by three characteristic refractive indices nx, ny, nz, along three corresponding axis x, y, z of index ellipsoid, x and y being situated inside the substrates plane, nx and ny being called in plane indices, with nx&#x2267;ny, x being called slow axis, and z being perpendicular to the substrates plane with biaxiality parameter Nz equal to (nx&#x2212;nz)/(nx&#x2212;ny), characterized in that Nz lies between &#x2212;&#x221e; and &#xbd; so that under oblique viewing the retardation of the stable texture corresponding to the dark state is compensated to improve the contrast ratio and simultaneously the retardation of the stable texture corresponding to the bright state is modified to decrease the color shift.

Single-polarizer reflective bistable twisted nematic (BTN) liquid crystal display device

A device nematic liquid crystal display device has two stable states corresponding to two liquid crystal molecule textures whose torsion differs by 150&#xb0; to 180&#xb0; in terms of absolute value. The device includes two polarizers (), one () of which is placed on the observer side, the other () being placed on the opposite side of the liquid crystal cell. The orientation of the two polarizers is offset by a value which is equal to the rotatory power of the cell+/&#x2212;&#x3a0;/2, the rotatory power corresponding to the most twisted texture effect.

Display device with a black-optimizing bistable nematic screen and method for the definition of said device

The invention relates to a nematic liquid crystal display having two stable states, without an electric field, obtained by anchoring break, characterized in that it comprises two polarizers (), one () of which is placed on the observer side, the other () being placed on the opposite side of the liquid crystal cell whereby the latter is at least partially reflecting in order to define a reflective mode or transflective mode. The orientation of the two polarizers () is offset by a value which is equal to the rotatory power of the cell at approximately +/&#x2212;30&#xb0;.

Display device with a white-optimizing bistable nematic screen and method for the definition of said device

A display device comprising a liquid-crystal cell element () placed between two polarizers () comprising at least one optical structure for compensating for the variations in birefringence of said liquid crystal according to the viewing angle. The optical compensation structure comprises at least one oblique-axis film () of polymerized liquid-crystal type suitable for at least partly compensating for the undesirable effects of the natural birefringence of the liquid crystal, combined with a volume hologram () of small retardation suitable for improving the compensatability of said film.

Liquid crystal display device with birefringence compensator and volume hologram

A document includes at least one drawing or data produced, for example, by printing. In addition, this document includes a hologram representing part of the document. The hologram of this document is recorded using a system including a prerecorded or electrically controllable optical modulator in which the image of at least part of the document is recorded. This modulator is designed to be combined with a layer of photosensitive material. A first reference wave illuminates the layer of photosensitive material. A second wave incident on the modulator and giving rise to a third object wave is also transmitted to the layer of photosensitive material in order to interfere with the reference wave in this layer.

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Orsay, France

Cécile Joubert