Bistable ferroelectric smectic liquid crystal display device having particular orientation film

Liquid crystal display device incorporating a tight cell inserted between two crossed rectilinear polarizers and comprising first and second insulating walls, whereof at least one is transparent, said walls being respectively coated by a first and a second electrodes with an appropriate shape for the display and between which is inserted a ferroelectric smectic liquid crystal film having parallel smectic layers and each constituted by chiral molecules having a longitudinal axis and a dipole moment perpendicular to said axis, the first and second molecules of each smectic layer being repsectively positioned facing the first and the second walls and means for producing between the first and second electrodes an electric field for orienting the dipole moment of the liquid crystal molecules, said device being characterized in that the first wall is covered by a first material able to orient, independently of the direction of the electrical field produced between the electrodes, the longitudinal axis of said molecules in a first direction forming an angle t with 0<t.ltoreq..theta. and with respect to a plane parallel to the walls and whose projection in said plane forms with a second direction contained in said plane an angle near to 0.degree., said first material comprising a film of at least one, substituted or unsubstituted long chain organosilane in contact with the liquid crystal film and deposited on a silica layer and/or optionally rubbed polymer layer able to form chemical bonds with the organosilane, and in that the second wall is covered with a second material able to orient the longitudinal axis of the molecules in a third direction parallel to said plane and whose projection in said plane forms with the second direction an angle near to +.theta. or -.theta., with respect to the direction of the electric field produced between electrodes.

Liquid crystal display device incorporating a tight cell inserted between two crossed rectilinear polarizers and comprising first and second insulating walls, whereof at least one is transparent, said walls being respectively coated by first and second electrodes with an appropriate shape for the display and between which is inserted a ferroelectric smectic liquid crystal film having parallel smectic layers and each constituted by chiral molecules having a longitudinal axis and a dipole moment perpendicular to said axis, the first and second molecules of each smectic layer being respectively positioned facing the first and the second walls and means for producing between the first and second electrodes an electric field for orienting the dipole moment of the liquid crystal molecules, said device being characterized in that the first wall is covered by a first material able to orient, independently of the direction of the electrical field produced between the electrodes, the longitudinal axis of said molecules in a first direction forming an angle t with 0<t.ltoreq..theta. and with respect to a plane parallel to the walls and whose projection in said plane forms with a second direction contained in said plane an angle near to 0.degree., said first material comprising a film of at least one, optionally rubbed, long chain organosilane in contact with the liquid crystal film chosen from the group consisting of octadecyl-triethoxysilane (ODS), dimethyl-octadecyl-aminopropylsilane (DMOAP) and their mixtures, and in that the second wall is covered with a second material able to orient the longitudinal axis of the molecules in a third direction parallel to said plane and whose projection in said plane forms with the second direction an angle near to +.theta. or -.theta., with respect to the direction of the electric field produced between electrodes.

Liquid crystal display device incorporating a tight cell inserted between two crossed rectilinear polarizers and comprising first and second insulating walls, whereof at least one is transparent, said walls being respectively coated by first and second electrodes with an appropriate shape for the display and between which is inserted a ferroelectric smectic liquid crystal film having parallel smectic layers and each constituted by chiral molecules having a longitudinal axis and a dipole moment perpendicular to said axis, the first and second molecules of each smectic layer being respectively positioned facing the first and the second walls and means for producing between the first and second electrodes an electric field for orienting the dipole moment of the liquid crystal molecules, said device being characterized in that the first wall is covered by a first material able to orient, independently of the direction of the electrical field produced between the electrodes, the longitudinal axis of said molecules in a first direction forming an angle t with respect to a plane parallel to the walls and whose projection in said plane forms with a second direction contained in said plane an angle near to 0.degree., and in that the second wall is covered with a second material able to orient the longitudinal axis of the molecules in a third direction parallel to said plane and whose projection in said plane forms with the second direction an angle near to +.theta. or -.theta., with respect to the direction of the electric field produced between electrodes, said second material being chosen from the group consisting of polyamide and gold.