Abstract: A method for manufacturing a fluorescent display screen cathode including microtips, comprises a supporting plate bearing cathode conductors in meshed columns, a resistive layer bearing microtips, an insulating layer and a grid conductive layer in rows. The method comprises the step of simultaneously etching the three upper grid layer, insulating layer and resistive layer according to a single perforated pattern defining both the grid rows and the access resistance to the microtips through the resistive layer.

Abstract: A flat vacuum without pumping stem, for the manufacturing of display screens, comprises two plates made of glass, a sealing peripheral joint interrupted so as to provide an aperture for evacuation of the gases during manufacturing, a thin-film metallic pad disposed on each inner surface of the glass plates at the level of the aperture, and a sealing element made of metal having a low melting point disposed so as to contact the metallic pads.

Abstract: A microdot fluorescent screen having a reduced number of addressing circuits. This screen of N rows (16) is divided into k zones Z.sub.i, each of the N/k rows (16) belonging to N/k families of rows. The k rows (16) of the same family are electrically interconnected. Each zone Z.sub.i also comprises three series of N/k conductive bands (26) each. The bands (26) of a first series are covered by a material (28) luminescing in the red, the bands (26) of a second series are covered by a material (29) luminescing in the green and the bands (26) of a third series are covered by a material (30) luminescing in the blue. Each triplet formed by three bands (26) covered by material luminescing in the red, green and blue is aligned substantially facing a row (16) (grid). The bands (26) of each series in a zone Z.sub.i are electrically interconnected for forming three anodes A.sub.1,i, A.sub.2,i and A.sub.3,i.

Abstract: A microdot trichromatic fluorescent screen comprising two facing substrates. The first substrate supports cathode conductors provided with microdots, grids and an insulating layer separating the same. The second substrate supports three series of parallel conductive bands. The conductive bands of each series are electrically interconnected and covered with a material luminescing in one of the three primary colors red, green and blue. Each series of conductive bands corresponds to a red, green or blue anode. The production of this screen requires no positioning between the two substrates.

Abstract: A dot matrix liquid crystal display having segment electrodes and common electrodes, a segment driver circuit and a common driver circuit, a multi-level power source, sensor resistors connected in series to the supply voltage bus lines for the segment electrodes, amplifiers for detecting and ampifying the voltage drop in the sensor resistors, and capacitors for capacitively coupling the common electrodes and the amplifiers. When the segment voltage is changed, the voltage change is sensed through the sensor resister and is fed back to the common electrode to reduce the induced noise on the common electrode.

Abstract: Disclosed is a homeotropic liquid crystal display which comprises a pair of substrates and a nematic liquid crystal layer disposed between the pair of substrate to form a cell. The substrates have tilt orientation directions parallel to each other which are capable of orientating liquid crystal molecules homeotropically or pseudo-homeotropically at an angle range of from 0.degree. to about 20.degree.. The nematic liquid crystal layer has negative dielectric anistropy and contains no or a very small amount of chiral molecules. The cell has a response time shorter than the driving frame time, and a small gap and low viscosity so that the liquid crystal layer is not twisted at an "OFF" state but is spontaneously twisted only in an "ON" state in which a pulse voltage is applied to the cell.

Abstract: A process for regulating the brightness of a microdot fluorescent screen and apparatus for performing this process. The screen is of the matrix type and is addressed by a scan of the rows, a pixel being formed at each row-column intersection. For an illuminated pixel, for a selection time T of the corresponding row, a quantity of charges is emitted by the associated microdots. The brightness is regulated during the selection time of each row by controlling the quantity of charges emitted by the microdots of each pixel to be illuminated, the charge quantity being identical for each pixel.

Abstract: A dot matrix type liquid crystal display device having two groups of mutually crossing parallel electrodes sandwiching a liquid crystal layer, the electrodes of one group having an aperture at each electrode crossing area along the direction of and centrally at the electrode of the other group. The electric field at the aperture portion is constantly slanted to a predetermined direction to present uniform and wide stable display areas.

Abstract: A planar light source, comprises a vacuum enclosure (1) bounded by two parallel, insulating planar walls (3,4) and a side wall (2). On each of the planar walls and within the enclosure (1) is placed a conductive electrode (5,6) covered with an insulating layer (7,8) and at least one of these two wall-electrode-insulating layer assemblies is transparent. On one of the insulating layers (8) is placed a cathodoluminescent material layer (9). In the vicinity of the side wall (2) and externally of the two conductive electrodes (5,6) is provided an electron source (11) and a voltage source (10) is also provided for alternatively applying to the two conductive electrodes (5,6) two different potentials (V.sub.anode, V.sub.rest), so that the electrons emitted by the electron source are alternatively collected by the electrodes.

Abstract: Method for controlling a matrix display screen enabling its contrast to be adjusted as regards a liquid crystals screen and its luminosity as regards a fluorescent micropoints screen, said method consisting of periodically applying line conductors addressing signals V1 having for a certain period a value Vmax into an absolute value to be applied to column conductors of control signals. Addressing signals are applied to the line conductors, the durations of said signals having a value Vmax and are partially recovered for two consecutive lines.

Abstract: The invention relates to a polychrome screen comprising alternating regions (40A, 40B) of a first (A) and a second (B) dichroic display materials placed between first and second insulating walls (31, 33) and alternating regions (42B, 42C) of a second (B) and a third (C) dichroic display materials placed between the second and third insulating walls (33, 35); each region of the first material of the first layer being superimposed both on a region of the second material of the second layer and part of a region of the third material of the second layer and each region of the second material of the first layer is superimposed on the other part of the region of the third material of the second layer. The present invention more particularly applies to polychrome display cells with liquid crystals, such as those of the nematic or ferroelectric type, using both a multiplexed and non-multiplexed display mode.

Abstract: Active matrix screen for the color display of television images or pictures, control system and process for the production of the screen.The screen utilizes the electrically controlled birefringence effect and comprises an assembly having a nematic liquid crystal layer (2) with a positive optical anisotropy between an active matrix having transparent control electrodes (8) and a transparent counterelectrode (10) equipped with colored filters (13) and two polarizing means (12,14), which are complimentary of one another and are located on either side of the assembly. The optical path in the layer is at the most equal to approximately 0.6 micrometer. The system comprises means for amplifying the blue, green and red video signals, whereof the respective gains are regulated so as to be able to display a neutral white shade.

Abstract: Liquid crystal matrix display screens in an uncrossed bus-type architecture are characterized in that at each point of the matrix there is a storage capacitance (CS) constituted by a spacer conductor (18,19) connecting part of the point electrode (16,17) surface to the facing part of the counterelectrode (12,13) and at least one of the two electrodes (12 and 16, 13 and 17) is covered by a thin insulating layer (20,21 and 22, 23).

Abstract: Liquid crystal cell using the electrically controlled birefringence effect and processes for the production of the cell and a uniaxial medium or material of negative optical anistropy usable therein.The cell can comprise two crossed rectilinear polarizers, two glass plates provided with transparent electrodes and placed between said polarizers, a liquid crystal layer between the plates and, between a plate and a polarizer, a layer of a negative uniaxial thermoplastic polymer having its extraordinary axis perpendicular to the plates. This layer can be obtained by heating the polymer up to the isotropic state, under a uniform presure on the polarizers, cooling and eliminating the pressure. Application to the production of data display devices.

Abstract: A single signal is produced, which includes a pedestal and a ramp. This signal is supplied to a column control circuit which transmits the voltage to each column for a time which can assume a number of discrete values between t.sub.1, the pedestal duration, and T.sub.L, the addressing time of one row. For t.sub.1, the black level is obtained, for T.sub.L the white level and between them, various gray levels.

Abstract: Cell with a double liquid crystal layer using the electrically controlled birefringence effect and process for producing a negative optical anisotropy uniaxial material usable in said cell.The cell can comprise two crossed rectilinear polarizers, three glass plates provided with transparent electrodes and placed between said polarizers, two liquid crystal layers between the plates and, between a plate and a polarizer, a sheet of the medium, whose extraordinary axis is perpendicular to the plates. This sheet can be obtained by heating a thermoplastic polymer up to the isotropic state, under a uniform pressure on the polarizers, cooling and eliminating the pressure. The cell is designed in such a way that the molecules of the respective layers tilt in two directions forming the same angle with the homeotropy direction, when an exciting voltage is applied between the electrodes, said directions, viewed in projection on a plate, also being opposite in the main observation plane.

Abstract: The nematic liquid crystal cell weakly doped by a chiral solute and of the electrically controlled birefringence type. Doping is such that the resulting cholesteric liquid crystal twist exceeds approximately twice the thickness of the liquid crystal coating and is less than approximately 8 times said thickness. Moreover, one of the sides of the cell is to be exposed to incident light and at least on said side, the cell comprises an advantageously linear polarizer. Application to the production of displays for moving images or pictures.

Abstract: A matrix display device and control therefore applicable to liquid crystal displays incorporates two groups of row electrodes and two column electrodes per image element. Each row conductor is connected by k.times.m switches to m groups of k parallel electrodes of a first family and to m groups of k parallel electrodes of a second family which alternate with one another, in such a way that each switch is connected to an electrode of the first family, to an electrode of the second family and to the row conductor. An image element is defined by the overlap zone of two column conductors of a first and a second family with two groups respectively of k electrodes of a first and a second family connected by k switches to the corresponding row conductor.Application to liquid crystal display means.

Abstract: The invention relates to a three-dimensionally controlled liquid crystal matrix display having a low number of connections and transistors to its control process. The display comprises a first insulating wall covered with electrode rows, each formed from n aligned row strips, a second insulating wall covered with electrode columns, each formed by r aligned column strips, and a liquid crystal layer inserted between the electrode columns and the electrode rows. The row strips and the column strips are respectively grouped into p first and second packets of s parallel row strips, and of t parallel column strips, with p=n.times.r, s=m.times.n/p and t=q.times.r/p. Each row strip and each column strip is associated respectively with a transistor serving to interconnect the row strips and interconnect the column strips to form s row connections, t column connections, and p packet connections.

Abstract: A process for the sequential control of a liquid crystal display means having different optical responses in alternating and steady fields. This process consists of applying to one side of a first electrode an a.c. potential V.sub.1 and to the other side an a.c. potential V.sub.2, with V.sub.2 -V.sub.1 constant, so that only line Y parallel to the sides of the first electrode is exposed to a reference potential V.sub.0 ; applying to one side of a second electrode an a.c. potential V.sub.3 and to the other side an a.c. potential V.sub.4, with V.sub.4 -V.sub.3 constant, so that only the line X parallel to the sides of the second electrode, intersecting the first, is exposed to V.sub.0 ; and applying a d.c. potential V.sub.5 to the two sides of one electrode, so that liquid crystal zone XY defined by the intersection of lines X and Y is only subject to potential V.sub.5 and that outside the zone the liquid crystal is subject to an a.c.