Abstract: Cholesteric polarizer and the manufacture thereof. A broadband cholesteric polarizer is described, as well as a method of manufacturing such a polarizer. Said polarizer comprises an optically active layer of a polymer material having a cholesteric order, said material being oriented so that the axis of the molecular helix extends transversely to the layer. In accordance with the invention, the polarizer is characterized in that the pitch of the molecular helix in the layer is varied in such a manner that the difference between the maximum pitch and the minimum pitch is at least 100 nm. The optically active layers are preferably provided on substrates which bring about a conversion of circularly polarized light into linearly polarized light. Three different methods of manufacturing such broadband polarizers are described.
Abstract: A liquid crystal device having a cell structure comprising a pair of base plates and a smectic liquid crystal having cholesteric phase at a higher temperature side; the ratio (P/d) of the spiral pitch of the cholesteric phase (P) to the spacing between the pair of base plates (d) is 0.5 or more.
Abstract: A composite material includes a cholesteric liquid crystal; a polymer which is distributed in phase-separated domains and provides an effective form-retention property for the composite material; and an additional material which is dissolved in the cholesteric liquid crystal and maintains a cholesteric phase of the liquid crystal and bistability of a focal conic state and a planar state of the liquid crystal.
Abstract: A liquid crystal device is constituted by (a) a pair of base plates each having an orientation control film thereon, and (b) a liquid crystal composition interposed between the base plates. The liquid crystal composition comprises a mixture including at least one liquid crystal compound which has a temperature range in which it shows chiral smectic phase and at least one optically active substance which does not have a temperature range in which it shows chiral smectic phase. The liquid crystal composition has a temperature range in which it shows cholesteric phase and is placed in chiral smectic phase which has been formed through cholesteric phase on temperature decrease. The liquid crystal composition comprises liquid crystal molecules having long axes forming a pre-tilt in the chiral smectic phase.
Abstract: An illumination system comprising a reflector, a cholesteric filter and a depolarizer. The cholesteric filter is arranged between a radiation source and, in a display device, a display panel, and is selected to transmit radiation having a selected state of polarization in a selected wavelength range, while reflecting otherwise polarized radiation in that wavelength range. The depolarizer is disposed between the reflector and the cholesteric filter. Radiation reflected by the cholesteric filter is re-reflected to the filter by the reflector and, having been depolarized in the depolarizer, is transmitted to the extent it has the selected state of polarization in the selected wavelength.
December 17, 1996
Date of Patent:
February 24, 1998
U.S. Philips Corporation
Adrianus J.S.M. De Vaan, Paulus B.J. Schaareman
Abstract: A display device having an emitter, a direct-view display screen, a light-guiding member for guiding illumination light emitted from the emitter to the direct-view display screen, a light separating element for separating the illumination light selectively into a first and second polarized light component and transmitting the first light component and reflecting the second light component, a light converting member for converting the reflected second light component to a first light component, a reflecting plate for returning the converted first light component to the light separating element, and a half-wave film for rotating the vibration direction of the first polarized light component, thereby obtaining the illumination light.
Abstract: An electrically activated infrared filter utilizes a mixture of infrared absorbing dyes in liquid crystal which normally presents a substantial cross section of dye to absorb the infrared component of impinging light. Polarizing light to be parallel to the direction of liquid crystal alignment enhances the absorption of infrared components. In an alternative embodiment, a chiral additive to the liquid crystal solution increases the dye cross section density which, by absorption, attenuates a higher proportion of the infrared wavelengths. A predetermined voltage differential across the cell aligns the liquid crystal and dye molecules to the voltage gradient, presenting a substantially non-absorptive path to the infrared components of impinging light.
August 12, 1994
Date of Patent:
March 25, 1997
Kaiser Aerospace and Electronics Corporation
Abstract: A dual function electro-optical display device operates as a bistable display when driven at one voltage, and operates as a nematic display when driven at another voltage. In the first mode, the image in the display zone is formed by applying a first electrical signal to the device, and the image persists upon removal of the first electrical field. In the second mode, the image is formed by applying a second electrical signal to the device, and the image disappears upon removal of the second electrical signal. In a liquid crystal display, the liquid crystal fluid (9) is a blend of at least one liquid crystal nematic compound and at least one liquid crystal cholesteric compounds, and is maintained in a gap (4) between two substrates (1).