Hughes Aircraft Company

Gm Global Technolgoy Operations, Inc.

Delco Electronics Corporation

Anna M Lackner

J David Margerum

Leroy J Miller

John D Margerum

George W Smith

Willis H Smith, Jr

James L Kohler

Elena Ramos

Charles R Allison

Khoon C Lim

Nuno A Vaz

Wei-Yu Wu

Tsung Y Hsu

Elena Sherman

Paul J Seiler

Nuno Yaz

A liquid crystal is used as the phase modulating medium in a microwave phase modulating cell (20). Applied electric and/or magnetic fields transverse to the direction of wave propagation create a birefringence that changes the velocity of wave propagation and the index of refraction of the medium. The phase modulating cell (20) is used singly or in arrays to direct microwave beams.

Microwave phase modulation with liquid crystals

A composite material (20) has electrically conducting, elongated particles (22) dispersed in a liquid crystal (24). The index of refraction to microwaves is controllable by the application of a transverse electric field that aligns the liquid crystal material (24) and the particles (22). A phase modulating cell (31) is formed by placing the composite material (20) inside a microwave wave guide (32), with transverse electrodes (36) built into the sides of the wave guide (32). Another set of transverse electrodes or magnet pole pieces (30) can be provided to align the liquid crystal material (24) and the particles (22) in another direction, thereby switching the index of refraction of the cell (31). The particles (22) may be made of a ferromagnetic material, to permit magentic as well as electrical switching.

Liquid crystal-based composite material including electrically

A shaped voltage pulse is applied to a polymer dispersed liquid crystal (PDLC) cell to control its transmission characteristics. The voltage has an initially high level that substantially exceeds the PDLC's threshold voltage. The initial voltage duration is relatively short, and is followed by a gradual reduction of the voltage to a level less than the threshold voltage within a given time frame; the voltage is preferably reduced at a generally exponential rate. Fast response is obtained by setting the initial voltage substantially above the voltage level that corresponds to the desired transmission level in the steady state; the voltage decays from its initial level so that the PDLC transmission actually peaks at the desired range. The shaped waveform forces the PDLC to operate on a hysteresis curve along which the reduction in transmission is delayed as the voltage decays, thereby increasing the cell's optical throughput. The invention is particularly applicable to liquid crystal light valves.

Shaped voltage pulse method for operating a polymer dispersed liquid

A high contrast display is provided by illuminating a polymer dispersed liquid crystal (PDLC) display panel through opposite edges thereof. Light is scattered out the front of the panel from non-activated areas of the PDLC in which the refractive indices of the liquid crystal and polymer matrix materials are mismatched. For a direct view transmission mode display, the rear of the panel is blackened so that activated areas of the PDLC in which the refractive indices of the materials are matched transmit edge-illuminated and ambient light and appear black. For a reflection mode display usable in combination with projection optics, the rear of the panel is provided with a mirror surface, and ambient light is prevented from reaching the panel.

Edge-illuminated liquid crystal display devices

A method of forming a polymer dispersed liquid crystal (PDLC) film is disclosed which consists of forming a solution of LC dissolved in a monomer, photopolymerizing the solution to form a film having a dispersion of LC bubbles therein, establishing a correlation between the LC bubble size and selected characteristics of the film, selecting a LC bubble size corresponding to desired film characteristics, and controlling the conditions of photopolymerization to achieve said LC bubble size. The LC bubble size is controlled by means of the UV exposure intensity, exposure temperature, exposure wavelength, LC concentration and/or concentration of polymerization initiator. Correlations are noted between LC bubble size and the resulting film's threshold and operating voltages for optical transmission, contrast ratio, absolute transmissivity and electro-optical response times. Special types of films, including in situ gratings and holograms, are obtained by periodically varying the conditions of polymerization over the film to produce a corresponding periodic spatial variation in the LC bubble size; different processes used to achieve this result are noted. Films with LC bubbles in a new size regime that significantly decreases the operating voltage threshold, and with gradients in the bubble size, are also disclosed.

Polymer dispersed liquid crystal film devices

Liquid crystals are induced to assume a uniform tilted alignment in the absence of an applied field by treating the surface of a substrate to provide a desired tilted surface microstructure and free hydroxyl groups. A long chain alcohol having the formula ROH, where R is a carbon chain having at least about 6 carbon atoms therein, is chemically reacted with the tilted surface microstructure and the alkoxy groups derived therefrom are chemically bonded to the microstructure. Subsequently introduced liquid crystals assume a tilted-perpendicular alignment at a tilt angle of about 0.5.degree. to about 6.degree.. The liquid crystals exhibit a significantly greater photostability than has previously been achieved. The microstructure is preferably obtained by depositing sequential layers of SiO.sub.x at medium and shallow grazing angles, where x is from 1 to 2, with the substrate rotated 90.degree. between depositions.

Method for tilted alignment of liquid crystals with improved

A light emitting panel is formed of a transparent plastic substrate doped with fluorescent dye which absorbs incident light through a relatively large surface area and emits light of a longer wavelength out through one edge. The incident light may be ambient or produced by a fluorescent light source. The edge emitted light is optically coupled into an edge of a display panel, which may be a polymer dispersed liquid crystal display or a plastic panel having a display surface formed with an etched or printed pattern, grating or hologram. The substrate materials of the emitting and display panels, as well as an optical adhesive which joins the edges thereof, preferably have an essentially similar index of refraction which is larger than that of air causing light propagating through the panels to be internally reflected and exit the structure only through the pattern on the display surface. The display panel is preferably transparent in the absence of light incident on the emitting panel, and produces a display visible from only one direction upon application of incident light. The display panel may be constituted as a center-high-mounted stop light for an automotive vehicle.

Visual display device with fluorescent dye-doped edge-illuminating

Polymer dispersed liquid crystal film devices, and method of forming the

A liquid crystal cell useful in light valves is disclosed in which positive anisotropy liquid crystals are installed at an initial off-perpendicular alignment within the approximate range of 6.degree.-45.degree.. A light valve employing the cell is initially biased to a voltage approximately corresponding to a transmissivity peak; the selection of the exact bias voltage involves a trade-off between contrast and response speed. The cell surfaces are characterized by generally flat macrostructures and tilted surface microstructures, with an overcoat on the surfaces of a long chain alcohol with alkoxy groups derived therefrom bonded to the tilted surface microstructure. The alcohol molecules have the formula ROH, where R is a carbon chain having at least six carbon atoms therein.

Light valves with positive dielectric anisotropy liquid crystal and

Liquid crystals are induced to assume substantially perpendicular alignment on the surfaces of substrates used to fabricate electro-optical device by causing long chain alcohols to react in the vapor phases with surface OH.sup.- inherently found on oxide coatings provided on the substrates. The process facilitates liquid crystal alignment in prefabricated electro-optical cells.

Growing community of inventors

Los Angeles, CA, United States of America

Anna M Lackner