Abstract: A liquid crystal display device comprises a first substrate, a first alignment layer disposed on a surface of the first substrate, a second substrate, second alignment layer disposed on a surface of the second substrate, and a liquid crystal layer disposed between the first substrate and the second substrate. The alignment direction of the first alignment layer has a non-zero component in a first azimuthal direction in a first region of the alignment layer and has a non-zero component in a second azimuthal direction different from the first azimuthal direction in a second region of the first alignment layer. In consequence, in zero applied electric field across the liquid crystal layer, a first liquid crystal state is stable in a first volume of the liquid crystal layer defined by the first region of the first alignment layer.

Abstract: To improve switching times, especially at low temperatures, one or more reactive liquid crystalline compounds is added to a liquid crystal mixture used in an electrooptical system. The electrooptical system comprises a PDLC film comprising a liquid crystal mixture forming micro-droplets in an optically isotropic, transparent polymer matrix between 2 electrode layers. The reactive liquid crystalline compounds are of formula II, R′—G′—R″, wherein R′, G′ and R″ are as defined herein.

Abstract: A liquid crystal device such as a display comprises a twisted liquid crystal layer whose surface director orientation at a first surface is oriented in a first direction and whose surface director orientation at a second surface is oriented in a second different non-perpendicular direction. The layer is disposed, for instance, between a linear polarizer and a reflector. A retarder is disposed between the layer and the polarizer and compensates for residual retardation of the layer at a first voltage across the layer. For instance, the retarder has a retardation substantially equal to the residual retardation and an optic axis perpendicular to the bisectrix of the orientations.

Abstract: A liquid crystal display device comprises: a layer of a chiral liquid crystal material disposed between first and second substrates; and means for applying a voltage across the liquid crystal layer. A first region of the liquid crystal layer is an active region for display and a second region of the liquid crystal layer is a nucleation region for generating a desired liquid crystal state in the first region when a voltage is applied across the liquid crystal layer. The ratio of the thickness d of the liquid crystal layer to the pitch p of the liquid crystal material has a first value (d/p)A in the first region of the liquid crystal layer and has a second value (d/p)N different from the first value in the second region of the liquid crystal layer.

Abstract: To improve switching times, especially at low temperatures, one or more reactive liquid crystalline compounds is added to a liquid crystal mixture used in an electroptical system.

Abstract: A surface mode liquid crystal device is made by forming a cell containing a mixture of a liquid crystal and a pre-polymer. An electric field is applied across the cell to arrange the liquid crystal in a predetermined surface mode state, such as the V state in the case of a pi-cell configuration. The liquid crystal is held in this state by the field while the pre-polymer is polymerized or cross-linked, for instance by ultraviolet irradiation. The electric field is then removed. The polymer stabilizes the predetermined surface mode state, for instance preventing relaxation of the V state to twist or splay state in the pi-cell configuration.

Abstract: A reflective liquid crystal device comprises a polariser and a mirror between which are disposed several retarder. At least one of the retarders is a variable liquid crystal element whose optic axis is switchable so as to switch the device between a reflective sate and a non-reflective state. In the non-reflective state, the total retardance of the retarders between the polariser and the mirror is equal to an odd number of quarter wavelengths for a wavelength at or adjacent the middle of the visible spectrum.

Abstract: An electroptical system which between 2 electrode layers contains a PDLC film comprising a liquid crystal mixture forming micro-droplets in an optically isotropic, transparent polymer matrix, in which one of the refractive indices of the liquid crystal mixture is matched to the refractive index of the polymer matrix, which exhibits an electrically switchable transparency essentially independent of the polarization of the incident light, the precursor of the PDLC film of which comprises one or more monomers, oligomers and/or prepolymers and a photoinitiator, and is cured photoradically, the liquid crystal mixture of which comprises one or more compounds of the formula I in which the substituents are defined herein characterized in that the liquid crystal mixture additionally contains one or more reactive liquid crystalline compounds in order to obtain improved switching times especially at low temperatures.

Abstract: A color display includes a first layer of pixels, each of which has an independently controllable light attenuation so as to control the display intensity of each display pixel independently. A second layer of pixels is provided in which the color of each pixel can be independently controlled. Thus, each effective display pixel can be controlled, independently of the other pixels, with respect to its intensity and chrominance.

Abstract: An optical device of the present invention, includes: an anisotropic layer containing anisotropic molecules, and an alignment layer adjacent the anisotropic layer. The alignment layer serves to align the anisotropic molecules in an adjacent surface region of said anisotropic layer. The alignment layer also includes a twisted molecular structure so as to define a twisted optical retarder.

Abstract: A twisted liquid crystal device includes a liquid crystal layer and first and second alignment layers disposed in opposite sides of the liquid crystal layer. The first and second alignment layers have respective alignment directions which are mutually inclined. A first linear polarizer is disposed on the opposite side of the first alignment layer to the liquid crystal layer. Electrodes apply a variable voltage across the liquid crystal layer which has a twisted liquid crystal structure. The liquid crystal layer is arranged for operation in surface switching mode with first and second regions of the liquid crystal layer adjacent the alignment layers being mutually optically de-coupled so as to define, within the liquid crystal layer when in use, a pair of separate, active optical retarders having mutually inclined optic axes.

Abstract: A switchable liquid crystal device, for instance for use as a reflective display, includes a cell containing a helical polymer network and a nematic liquid crystal. Electrodes are provided for applying a field across the cell so as to switch between different optical states. In a reflective state, the cell reflects incident light within a waveband which is relatively insensitive to temperature variations. The device is formed by filling the cell with the liquid crystal and polymer precursor material and then cross-linking or polymerising, for instance by photopolymerisation, the precursor material to form the helical polymer network.

Abstract: A reflective liquid crystal device includes a polarising beam splitter, a polarisation preserving reflector and a retarder arrangement including at least two retarders. A first of the retarders is disposed between the beam splitter and the reflector, and a second of the retarders is disposed between the first retarder and the reflector, and at least one of the first and second retarder including a liquid crystal layer which is switchable between a dark device state and a bright device state. In the dark state, the retarder arrangement rotates the plane of polarisation of plane-polarised light directed by the beam splitter towards the reflector by substantially n.times.180.degree., where n is an integer, and in a bright device state the first retarder has a retardation of substantially .lambda./2 and the second retarder has a retardation of substantially .lambda./4.

Abstract: The invention relates to an electroptical system which, between 2 electrode layers, contains a PDLC film comprising a liquid crystal mixture forming micro-droplets in an optically isotropic, transparent polymer matrix. The liquid crystal mixture comprises one or more compounds of the formula I ##STR1## wherein Z.sup.1, Z.sup.2, ##STR2## X.sup.1, X.sup.2, Q, Y, n and R are as defined herein. The liquid crystal mixture additionally contains one or more reactive liquid crystalline compounds in order to obtain improved switching times especially at low temperatures.

Abstract: A twisted liquid crystal device includes a liquid crystal layer and first and second alignment layers disposed in opposite sides of the liquid crystal layer. The first and second alignment layers have respective alignment directions which are mutually inclined. A first linear polarizer is disposed on the opposite side of the first alignment layer to the liquid crystal layer. Electrodes apply a variable voltage across the liquid crystal layer which has a twisted liquid crystal structure and is arranged for operation in a surface switching mode with first and second regions of the liquid crystal layer adjacent the alignment layers being mutually optically de-coupled so as to act, within the liquid crystal layer, when in use, like a pair of separate, active optical retarders having mutually inclined optic axes and optical retardations which can be varied within a range to cause color.

Abstract: A polarization independent optical phase modulator comprises first and second substrates. A reflector is disposed between the first and second substrates and a quarterwave plate is disposed between the reflector and the first substrate. A polarization dependent electrooptic layer is disposed between the quarterwave plate and the first substrate. The quarterwave plate has an optic axis which is aligned at 45 degrees to the polarization whose phase is modulated by the electrooptic layer.

Abstract: A twisted nematic liquid crystal device has a liquid crystal layer between a pair of alignment layers. Glass plates with electrodes are disposed on opposite sides of the layers. The alignment layers have their alignment directions disposed mutually perpendicular and at .+-.45.degree. with respect to adjacent linear polarizers. The pretilt angle of liquid crystal molecules in a surface region of the layer adjacent the alignment layer is different to that of liquid crystal molecules in a surface region of the layer adjacent the alignment layer.

Abstract: An electrooptical system is disclosed in which a PDLC film is positioned between 2 electrode layers. The PDLC film contains a liquid crystal mixture forming microdroplets in an optically isotropic, transparent polymer matrix. The liquid crystal mixture comprises one or more compounds of formula I ##STR1## wherein R, A.sup.1, A.sup.2, Z.sup.1, Z.sup.2, X.sup.1, X.sup.2, Q, Y and n as herein defined, and one or more reactive liquid crystalline compounds. The PDLC film exhibits improved switching times, especially at low temperatures.

Abstract: A patterned polarization-rotating optical element includes a layer of birefringent material having a thickness d and birefringence .DELTA.n, wherein the layer includes at least one first region and at least one second region, at least one of the first and second regions comprising twisted birefringent material having a fixed twist angle .phi. such that .DELTA.n.multidot.d>>.phi..multidot..lambda./.pi., where .lambda. is a wavelength in vacuum of optical radiation, so that the at least one first region provides a first fixed angle of rotation of polarization of light and the at least one second region provides a second fixed angle of rotation of polarization of light, the second angle being different from the first fixed angle.

Abstract: A liquid crystal display includes glass cell walls on which are formed alignment layers. The cell is filled with liquid crystal material, such as FLC material. Chemical bonds are formed between the alignment layers and the adjacent liquid crystal layers so that the liquid crystal layers are bonded to the alignment layers in order to increase resistance to mechanical damage.