Abstract: A method of fabrication of a control transistor for a flat-panel display screen involves the following steps:deposition of conductive material such as ITO on a substrate;etching of electrodes in the conductive material;successive depositions of layers formed of metallic material followed by n-doped amorphous semiconductor material;etching of a column and a connecting element in contact with the electrode;successive depositions of layers formed of undoped amorphous semiconductor material followed by insulating material and then by metallic material;etching in the three layers which have just been deposited of a row which overlaps the column and the connecting element.

Abstract: The invention relates to controlling a matrix access display device comprising a layer of material reacting to a combined thermal and electric effect. According to the invention, the DC video control voltage is transformed into an AC voltage by switching the potentials of the electrodes applying the electric control field.

Abstract: The invention relates to display devices with a mixed thermal and electrical effect. The invention relates to a special addressing mode making it possible to display a writing line, while limiting the control voltages to be applied from the outside to the display screen.

Abstract: The present invention relates to cells using a smectic phase liquid crystal film and provides in the same cell two addressing modes: optical addressing by means of a laser beam and matrix addressing by means of heating electrodes.

Abstract: The invention relates to an organic compound obtained by synthesis from 3,5-dihydroxybenzoic acid. The compound according to the invention is in accordance with the following general formula: ##STR1## in which R stands for an organic group of the alkyl, alkoxy or alkyl carboxylate type having 1 to 15 carbon atoms and in which X designates a nitrile or halogene group.

Abstract: The invention relates to matrix access display devices using a mixed thermal and electric effect and provides a display device with mixed thermal-electric drive using a smectic liquid crystal deprived of a nematic phase by addition of appropriate dopes.

Abstract: A process wherein certain disc-like liquid crystals, which locally undergo heating and then rapid cooling on either side of the transition temperature between two mesophases permit the liquid crystal to become diffuse with an adequate contrast to be used for display purposes. The following liquid crystals can be utilized, i.e.

Abstract: The invention relates to planar display screens and more particularly to smectic liquid crystal screens.One of the problems of high definition display screens (approximately 100 to 1000 lines and columns) is caused by the devices for controlling the heating current on the lines. The complexity of the installation and costs limit the increase in the definition. The invention arranges the N lines of a screen into .sqroot.N groups of lines supplied at each of their ends by .sqroot.N control devices functioning sequentially, i.e. 2.sqroot.N devices in all. Moreover, each line has a diode placed between the heating resistor and the common point of the circuit.Application to the display of images transmitted in the form of a video signal for television and display peripheral equipment in teletransmission.

Abstract: An electro-optical display device which comprises a twisted nematic liquid crystal layer and a photo-conducting layer. Two crossed electrode assemblies allow the liquid crystal to be made transparent at the points to be displayed. The light which passes at these points makes the photo-conductor conducting which applies the whole of the voltage to the liquid crystal and gives greater rapidity of inscription and a memory effect.

Abstract: A liquid crystal visual display with a liquid crystal layer between two plates and resistive lines between one of the plates and the liquid crystal layer for heating the crystal to produce a display. The thermal diffusivity of the plate supporting the lines is below a value making possible viewing with the naked eye, for example 2.times.10.sup.-2 cm.sup.2 /s.

Abstract: A display device having a memory making it possible to display information supplied by electric signals and to maintain this display when the signals have disappeared. In a smectic liquid crystal display cell the two plates enclosing the liquid crystal layer can be moved apart by a piezoelectric wedge so as to make the crystal diffusive throughout. Parts of this crystal are then made transparent by applying thereto a reorientation electric field by means of a set of electrodes. The device is intended for use more particularly in telephone exchanges having a device for the display of digital data transmitted on a telephone line.

Abstract: The invention provides an image converter device which utilizes a liquid crystal cell in which a layer of a nematic material or a nematic-cholesteric mixture is enclosed between a first plate of a photoconductive material, provided with an external electrode, and a second transparent plate, provided with an internal electrode. The photoconductive material may be bismuth oxide, or a mixture of the latter with germanium or silicon oxide. A direct or alternative voltage is applied between the electrodes. An X-rays image, or an image displayed on the screen of a C.R. tube is projected onto the photoconductive plate whose conductivity, thus spatially modulated, causes a spatially variable voltage to be applied in the liquid crystal layer.

Abstract: A device for visualizing an image on a large screen with a small projection distance, in which the image is formed by pieces on an assembly of liquid crystal cells for then projecting it onto a visualization screen by means of an assembly of lenses associated with the liquid crystal cells; to illuminate the cells a transparent plate is used forming a light-guide and which comprises an assembly of networks associated with the cells to extract the light from the plate and project it onto the cells.

Abstract: The invention provides a liquid crystal imaging system which employs a transitory thermo-optic effect to permit notably the reproduction of T.V. images. This transitory effect is characterized by the fleeting appearance of scattering cybotactic zones in the transparent liquid phase of a mesomorphic material, at the very beginning of the transition to a nematic transparent ordered phase. The duration of the scattering period can be considerably shortened by subjecting the mesomorphic material layer to the action of an alternating electrical field.

Abstract: This invention relates to an optical apparatus for the reproduction of images, comprising an optical modulator formed by a nematic liquid crystal cell the length of which is at least equal to the width of the paper to be printed, comprising on an inner surface N electrodes corresponding to the N points forming a line and a counter electrode on the other surface, this cell being placed between two polarizers. The modulator produces or does not produce extinction of the radiation for each point, depending on whether a voltage is not or is applied between the counter electrode and the electrode corresponding to the point which is to be reproduced. The light-sensitive paper travels against the second polariser and is printed by a line of light modulated spatially along the N points. To ensure that the optical modulator thus produced functions satisfactorily, the light source should flash on when the liquid crystal has reached a stable state, i.e.

Abstract: A telecopying process and a transmitter-receiver telecopier employing this process. A cell having a smectic liquid crystal is used for recording by thermo-optically forming an intermediate image of a linear element (column portion or a whole line) of the transmitted document, which image is thereafter projected onto a photosensitive surface. The same optical system permits, when transmitting, the reading of this linear element by a mosaic of detectors and, when receiving, the projection onto the photosensitive surface of the intermediate image recorded in the cell.

Abstract: A system comprising means for emitting an analysis beam and a recording beam, the two beams being deflected by common deflection means. The analysis beam scans the document carrying the image to be analyzed and a detecting photocell provides an electrical signal. The recording beam scans a liquid crystal cell, where it records the image in synchronism with analysis in dependence upon a modulation of the thermo-optical effects induced in the liquid crystal. This modulation is provided by the electrical signal.

Abstract: In a liquid-crystal display device, a smectic liquid-crystal layer and a layer of photoconductive material are placed between two transparent plates. A voltage is applied to the photoconductor by means of electrodes while scanning the photoconductor with a writing light beam. At locations in which the resistance of the photoconductor is reduced under the action of the light beam, the heat generated causes transition of the liquid crystal to the isotropic state. The light-scattering action produced by subsequent cooling of the liquid crystal has the effect of writing the image to be displayed.

Abstract: A device for displaying a television video signal comprising a liquid-crystal layer inserted between two substrates. A plurality of heating lines deposited onto one substrate heats successively the layer up to an erasure temperature. A plurality of columns apply to the liquid crystal layer during the cooling of each line, samples of a video signal representing the image to be displayed. The lines of the image are thus recorded one after the other and all the dots of one line are simultaneously recorded thus allowing the layer to be heated and cooled along one line during the duration of one TV line scan.

Abstract: The invention provides a liquid crystal display cell in which particles having a preferential light absorption direction, particles which may be the molecules of a dichroic pigment, are inserted in the body of a layer of a mesomorphic material in a smectic state. The write-in can be made by a thermo-optical process. The molecular orientation of the smectic material controls the particles orientation, so that the variation in the light scattering coefficient commonly used with smectic layers are replaced by variations in the absorption coefficient, easier to use and provide a better contrast.