EP0592327A1 - Elektrochemisches Verfahren zur selektiven Herstellung und Differentialzüchtung einer festen Phase. Anwendung an Matrixanzeigern - Google Patents

Elektrochemisches Verfahren zur selektiven Herstellung und Differentialzüchtung einer festen Phase. Anwendung an Matrixanzeigern Download PDF

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EP0592327A1
EP0592327A1 EP93402488A EP93402488A EP0592327A1 EP 0592327 A1 EP0592327 A1 EP 0592327A1 EP 93402488 A EP93402488 A EP 93402488A EP 93402488 A EP93402488 A EP 93402488A EP 0592327 A1 EP0592327 A1 EP 0592327A1
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voltage
image
cells
phase
columns
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French (fr)
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Bernard Warszawski
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Alpine Polyvision Inc
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Alpine Polyvision Inc
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/38—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using electrochromic devices

Definitions

  • the invention relates to a process for the selective formation and differential growth of a new solid phase by electrochemical means.
  • the present invention applies to a multiplicity of cells in which the formation and development is carried out, that is to say the growth of a solid phase by electrochemical means. It applies in particular to devices in which the formation and development of such a solid phase by electrochemical means are used to modulate an optical density by reflection or by transmission, or are combined with the formation and development of another species used for such modulation. It applies in particular to devices such as flat display screens and more particularly to display devices called matrix screens, that is to say comprising a regular matrix of image points allowing the representation of alphanumeric characters, graphics, still images, moving images (when the renewal frequencies allow them), etc.
  • the information content or information representation capacity of a display screen can be characterized as a first approximation by its number of image points ("pixels"). This is for example of the order of a thousand to a few tens of thousands for a low-end display for representing alphanumeric characters, 300,000 for a black and white computer screen and 900,000 for a color screen. , 1,500,000 for a color television screen and 4 million for a high definition television screen (HDTV). Each image point of a screen must be able to be addressed individually in order to be brought to the optical density or to the luminance which is that of the point considered at a given instant in the image represented.
  • pixels image points
  • the most common multiplexed addressing method of a matrix screen requires that in a matrix of mxp image points, the elementary cells generating these image points be placed at the intersections of m conductive lines and p conductive columns, so as to be able to control them with only m + p control circuits each actuating a row or a column.
  • the elementary generator cell of an image point comprises at least a first electrode and a second electrode, at least one of which is transparent in a display operating by reflection, and both of which are transparent in a display operating by transmission.
  • An electrical voltage or an appropriate voltage variation applied to the electrodes makes it possible to modify the optical density of the image point and to modulate the light that it reflects or transmits.
  • a matrix screen is constituted by a matrix of image points whose elementary generating cells are located at the intersection of two orthogonal networks of electrical conductors: a network of m parallel lines between them each of which connects between they all the first electrodes of the elementary cells located on this line, and a network of p columns parallel to each other, each of which connects to each other every second electrodes of the elementary cells located on this column.
  • the mxp image points are addressed and controlled via m + p control circuits each actuating a row or a column and applying to it a particular profile of voltage as a function of time.
  • the most common multiplexed matrix addressing method is to wipe the screen line by line, applying between the line considered and each of the columns simultaneously an appropriate potential difference producing the writing of the only selected image points located on this line; the scanning of the screen then starts again in the same way, either to maintain the contrast, compensate for losses, etc., or to change the image.
  • Other methods exist, which use more complex diagrams of applying voltages to rows and columns.
  • This structure of the matrix screen comprising the reduction of the number of control circuits to substantially twice the square root of the number of image points is however not capable of allowing multiplexed matrix addressing or only allows it with defects (low contrast, low angle of view, diaphoty, etc.) if the electro-optical phenomenon generating the image does not present or only exhibits certain particular characteristics.
  • a first characteristic essential for matrix addressing is that the electro-optical phenomenon generating an image (that is to say a generator of luminance, of optical density) has a defined threshold of writing voltage, that is to say ie has a voltage threshold below which an image point cannot be written: in the absence of such a threshold, it is not possible to selectively write only the selected image points of the matrix.
  • this writing voltage threshold is close to the effective writing voltage: as via the common conductors of lines and columns the non-selected image points are also subject to parasitic voltages, they can, if the threshold is too low or poorly defined, also be written partially (crosstalk) and the contrast is degraded.
  • electrochemical or electrochromic processes use the reversible change in color and / or optical density obtained by electrochemical redox of a so-called electrochromic material whose oxidized form and reduced form, which form a couple reversible redox, are of different colors and / or optical densities.
  • electrochromic solids which are generally solids insoluble in the two oxidation states between which they change colors. Mention may be made, for example, from inorganic solids, WO3, MoO3, V2O5, Nb2O5 , IrO x , etc. (an extensive list is given for example in document US-A-3,704,057).
  • the change of state of the most used solid, WO3, colorless is its reduction into a blue solid of the form M x WO3 which is obtained by electrochemical insertion of alkaline cations, for example Li+, or of protons, in the WO3 network.
  • Inorganic solids such as lutetium diphthalocyanine, behave similarly.
  • Other solids, such as IrO x or Prussian Blue pass from the colorless state to a colored state by anodic oxidation which is accompanied by the injection of protons in the lattice of the first solid and of K c cations in the network of the second.
  • a particularly interesting class is that of conductive, electroactive or redox polymers: polyaniline, polyacetyline, polypyrrole, polythiophene, etc. which also change state by oxidation-reduction with insertion-disinsertion of dopants in the polymer (Kaneto et al, J. Appl Phys., 61 (3), 1 Feb 1987).
  • Another class is that of metal-metal ion couples where the optical density is obtained by electrocrystallization of a metal, for example silver (J. DUCHENE et al, IEEE Translations on Electron Devices, vol RD-26, N ° 8, August 1986, p 1263).
  • the elementary cell of an electrochromic or electrochemical display device generally comprises a transparent front electrode deposited on a transparent plate of glass or plastic material, in contact with which is an electrochromic material in the form solid layer in its two states, or in solid form in one of its states and dissolved in the other, etc., an interval filled with electrolyte, a second electrode or counter-electrode (also transparent if the device operates by transmission) and conductors for connecting each electrode to the control electronics outside the cell. It also includes a second redox couple present at the counter electrode which undergoes the combined electrochemical reaction of that which occurs at the working electrode: cathodic reduction combined with anodic oxidation, and vice versa.
  • This second redox couple can contribute in certain embodiments to the chromogenic reaction which occurs at the working electrode.
  • Habib et al. J.Appl. Electrochemistry, 21, (1991), 203-207 describes an electrochromic display cell which presents two couples each having electrochromic properties which add up: tungsten trioxide and Prussian blue.
  • the electrochromic material passes from the state with low optical density and / or low coloring to a state with higher optical density and / or stronger coloring.
  • the electrochromic material undergoes the reverse transformation.
  • Electrochromic light modulation processes have a set of remarkable characteristics for many applications: low control voltage, at most a few volts, which allows the use of control electronics and low cost addressing; low energy consumption; open circuit memory; relatively uncritical interval between electrode and counter-electrode. They also have additional characteristics which are particularly advantageous for display devices: very high contrast, even in lateral vision at a high angle; excellent visibility by reflection in conditions of strong illumination such as outside in strong sunlight; extended gray scale; important range of operating temperatures, often extending to low temperatures. In addition, the low energy consumption allows applications where autonomous operation (on batteries or accumulators) is required.
  • Electrochromic or electrochemical displays indeed have additional specific constraints with regard to matrix addressability: not only should they have a well-defined writing voltage threshold, as close as possible to the actual writing voltage, but also the image point should also have a circuit memory coupled (called by various authors “short-circuit memory”), that is to say a memory under load preventing the written picture points from partially discharging in the unwritten picture points to which they are necessarily electrically coupled via the common row and column conductors of the matrix.
  • the written picture points have a potential difference or electromotive force that unwritten picture points do not have, and they tend to discharge there until equilibrium, writing them down partially while losing part of their writing load; the selected and non-selected image points then have a neighboring optical density and the contrast becomes unacceptably low.
  • Such a coupled circuit memory is fundamentally different from the open circuit memory that almost all electrochromic or electrochemical displays have. The absence of such a memory under load makes it possible to maintain practically no contrast on an electrochromic matrix screen even if there is a writing voltage threshold making it possible to selectively write the selected image points.
  • Arellano et al SID 78 Digest, p22 selectively discharge the written picture points through the control circuits which have a low impedance compared to those of unwritten picture points, but obviously have to permanently recharge the selected image points, at a frequency of 33 Hz, which results in considerable consumption of electrical energy.
  • a first object of the present invention is, for a system comprising a multiplicity of electrolysis cells, a method of selective formation and differential growth by electrochemical route of a new solid phase in each cell of a selected fraction of this multiplicity cells.
  • a second object is a multiplexed matrix addressing method for electrochromic and electrochemical matrix screens making it possible to solve the problems encountered in the prior art without using an active matrix, and making it possible to operate such screens with new speed properties. and contrast.
  • Another object of the present invention is, for a system comprising a multiplicity of electrolysis cells whose electrodes are electrically coupled together by a network of electrical conductors such that they make it possible to control any particular cell, a method selective and differential sensitization of cells making it possible to induce electrochemically the selective and differential development, that is to say the selective and differential growth of a new solid phase in a chosen configuration of cells to the exclusion of others.
  • Another object of the present invention is, for a system comprising a multiplicity of electrolysis cells, a method of differential growth rapid of a new solid phase in a chosen configuration of sensitized cells to the exclusion of others.
  • Another object of the present invention is, for a system comprising a multiplicity of electrolysis cells, a method of differential maintenance assisted by the new solid phase developed now this phase in a chosen configuration of cells to the exclusion of the others.
  • Another object is a method for addressing and writing an electrochemical or electrochromic matrix display screen which does not require an active matrix, comprising the development of a writing threshold allowing discrimination between selected image points and unselected image points, of a memory in coupled circuit of written image points avoiding the partial discharge of the latter in the unwritten image points and the resulting loss of contrast, as well as the differential assisted maintenance of the only image points writings.
  • Another object is a method for quickly addressing and writing an electrochromic or electrochemical matrix display screen which does not require an active matrix, making it possible to write the screen in a single time according to an image comprising a scale of gray, maintain the displayed image without flickering for the entire duration of the planned display, and clear the screen in a single time to change the displayed information, a process allowing high frequencies of image renewal allowing their animation .
  • the electrolysis voltage is applied gradually according to a preferably linear increasing ramp; the voltage of the sensitization pulse is modulated to obtain differential growth of the new phase from one cell to another; the electrochemical reaction comprising the formation of a new phase is the electrocrystallization of a metal or of an alloy by cathodic reduction of ions in solution; electrocrystallization of the metal or of the alloy is carried out on a semiconductor electrode, in particular a tin oxide (TO) or mixed tin and indium oxide (ITO) electrode transparent thin layer; the new electrocrystallized phase is bismuth or copper or a bismuth or copper alloy.
  • a semiconductor electrode in particular a tin oxide (TO) or mixed tin and indium oxide (ITO) electrode transparent thin layer
  • the new electrocrystallized phase is bismuth or copper or a bismuth or copper alloy.
  • the electrochemical process generating optical density is the electrocrystallization of a metal or alloy by reduction cathodic of ions in solution, in particular electrocrystallization of bismuth or of a bismuth or copper alloy or of a copper alloy;
  • the electrochemical process generating optical density is the electrocrystallization of a metal or alloy by cathodic reduction of ions in solution on a glassy or amorphous electrode, in particular tin oxide (TO), indium oxide, l 'mixed indium tin oxide (ITO);
  • the voltage of the awareness pulse of an image point is modulated according to the level of gray or black that the image point considered must present;
  • the redox couples involved in the electrochemical reactions of the cells are chosen so as to present a difference in their redox potentials, so that the cells exhibit an electromotive force when the image points they generate are written; one compensates for any weakening of the writing load
  • the expressions "a new solid phase” and “one of the electrochemical reactions” have been used, but the invention also includes the case where several new solid phases are formed simultaneously and the case where the two conjugated electrochemical reactions are concerned when the electric current flows in one of the two directions.
  • the present invention applies to an electrolysis cell and to a multiplicity of electrolysis cells on at least one electrode, each of which the electrochemical reaction involves the formation and growth of at least one new solid phase when the electric current passes in one direction (and the absorption of this new phase when the electric current passes in the opposite direction). It applies in particular to an electrochemical cell and to a multiplicity of electrochemical cells in which one proceeds to the electrocrystallization of a metal or metallic alloy or of a solid composition by cathodic reduction, or to the formation of an oxide or of another metallic compound by anodic oxidation, or else at the insertion or intercalation or at the disinsertion or disintercalation of an ion in the network of a metallic compound or of an electroactive polymer.
  • electrochemical cells constituting the cells generating image points of so-called electrochromic display devices in which the generation of the optical density of the image point is carried out by electrocrystallization of a metal, metal alloy or composition solid such as diheptyl-viologene, electrocrystallization of a metal oxide or other metallic compound, insertion or doping or desinsertion or dedoping of an ion in the network of a metallic compound or of an electroactive polymer on the transparent electrode seen by the observer.
  • electrochemical reactions such as the preceding ones occurring on the second electrode without the latter necessarily participating in the generation of the optical density.
  • this is for example the case of cells operating by reflection in which the two electrodes are separated by an opaque material, for example a reflector or an opaque white reflecting pigment. It applies in particular to flat screen display cells and devices described in patent applications No. FR-2 618 566, No. FR-2 618 567, No. FR-2 669 121 in which the increase optical density is obtained by the cathodic reduction of ions in solution in an electrolyte consisting of an aqueous solution gelled in a metal or alloy which electrocrystallizes on a transparent electrode, and the reduction in optical density is obtained by the reverse electrochemical reaction: anodic oxidation of this metal or alloy into ions in solution.
  • This new phase can be a metal or alloy resulting from the cathodic reduction of an ion in solution, an oxide resulting from the anodic oxidation of a species dissolved in solution (for example PbO2 from a nitrate solution), a metal salt resulting from the oxidation of a metal (for example PbSO4 formed from lead during the discharge of a lead accumulator), a metal salt resulting from the reduction of another oxide (for example PbSO4 formed by the reduction of PbO2 from the positive electrode during the discharge of a lead accumulator), or a gas (for example chlorine in a chlor-alkali electrolyser), or of solid Li x WO3 obtained by intercalation electrochemical of Li+ ions in the tungsten trioxide network WO3, or alternatively polythiophene doped by electrochemical injection of a dopant in the undoped polymer.
  • a metal or alloy resulting from the cathodic reduction of an ion in solution
  • Such reactions involving the formation of a new solid phase frequently have a unique characteristic: the current-voltage characteristics before and after the formation of the new phase are different: it is for example well known that the current-voltage characteristic (curve of polarization) of the cathodic deposition of copper from a solution of copper ions on an inert graphite electrode is significantly different from that of the same electrochemical reaction if the graphite electrode is already covered with a thin layer of copper.
  • This situation results from the fact that the formation of a new phase requires the nucleation of seeds of this new phase, a thermodynamically irreversible process which requires substantial additional activation energy to occur, that is to say a substantial overvoltage. Once these germs or nuclei are formed, their growth can continue without requiring this overvoltage.
  • this new phase is generally an electrode which does not participate in the electrochemical reaction (for example of the '' tin oxide or mixed oxide of indium and tin used as transparent electrode in flat screens); it can also be the solid phase from and in which the new phase develops (solid electronic conductors such as tungsten trioxide or electroactive polymers such as polythiophene, polyaniline, polyacetylene, which change oxidation state with insertion or intercalation of ions, etc., in their network or conversely disinsertion or deintercalation of these ions or etc).
  • solid electronic conductors such as tungsten trioxide or electroactive polymers such as polythiophene, polyaniline, polyacetylene, which change oxidation state with insertion or intercalation of ions, etc., in their network or conversely disinsertion or deintercalation of these ions or etc).
  • the new phase generally has a crystallographic structure and a morphology different from that on the surface or inside of which it develops. Its nucleation therefore cannot generally be carried out in epitaxial relation with this support or in continuity with the network from which it develops. It therefore requires that the first germs form with a distortion of their network, that is to say at a higher energy level than the normal network; the supply of this additional energy during the electrochemical reaction is expressed by an overvoltage. As the germs develop, the network is less and less deformed, and the growth continues without requiring this overvoltage. The greater the difference between the crystal structures and, more generally, the morphologies of the new phase in formation and of the support phase, the higher the overvoltage of nucleation.
  • the electrolysis during which at least one of the two electrochemical reactions involved involves the formation of a new phase, in particular a new solid phase, can only begin to occur if the applied voltage is momentarily greater than a threshold.
  • This electrolysis voltage threshold is at least equal to the sum of the minimum electrolysis voltage and the nucleation overvoltage of the new phase (s). This threshold may be higher, other temporary thermodynamic irreversibilities contemporaneous with the nucleation of the new phase may affect the course of one and / or the other of the two electrochemical reactions.
  • electrolysis can continue with a voltage lower than the threshold, which can be as low as the minimum electrolysis voltage.
  • the method allowing the formation and growth of the new phase in the only cells selected in the system and vice versa, the absence of formation and development of the new phase in the cells not selected in the system.
  • a system comprising a multiplicity of electrolysis cells in which at least one of the electrochemical reactions produced by the passage of an electric current comprises the formation of a new solid phase with a substantial overvoltage of nucleation
  • use the temporary nature of this nucleation overvoltage to obtain the selective formation and growth of said new phase in each cell only of a selected fraction of the cells of the system, although applying the same electrolysis voltage to all cells in the system simultaneously.
  • first apply a voltage pulse above the electrolysis threshold to the selected cells only then apply to all cells an electrolysis voltage below the electrolysis threshold: we then observe in the cells only selected training and growth of the new phase.
  • the duration of the pulse required to produce sensitization can vary from a few microseconds, or even less, to several milliseconds.
  • an electrolysis voltage applied simultaneously to sensitized cells and to non-sensitized cells selectively develops the new phase in the former. Everything happens as if the sensitization pulse sensitized the cells so as to allow a subsequent selective development of the new phase.
  • a parallel can be drawn with the photographic processes in which the sensitization of a photographic photograph by short-term illumination allows the subsequent selective development of the silver image in the illuminated regions.
  • the sensitization pulse creates in cells an "electrochemical" latent image "developable” by electrolysis, to compare with the latent image created in a photographic photograph by illumination and chemically developable by a reducer.
  • This electrochemical "latent image” is in all likelihood constituted by nuclei or seeds of the new solid phase nucleated by the sensitization pulse, the invention however not being linked to this hypothesis.
  • the voltage of the sensitization pulse can be modulated in order to obtain differential growth of the new phase from one cell to another.
  • the aforementioned awareness is to be reconciled here again to understand the invention is only for this reason, in the latent image in photography: everything happens in fact as if the number of nuclei or germs developable created by the awareness pulse was as a function of the voltage of this impulse, just as in photography it is a function of illumination. Indeed, by applying to cells having undergone sensitization pulses with different voltages the same electrolysis voltage for the same duration, a differential growth of the new phase is observed: the morphology of the new phase appears different from a cell to cell. It has therefore been found that the method according to the invention allows differential sensitization resulting in differential growth.
  • electrolysis cells in which at least one of the electrochemical reactions produced by the passage of an electric current comprises the formation of a new solid phase with a substantial overvoltage of nucleation exhibited once written memory in coupled circuit.
  • This coupled circuit memory is developed during the implementation of the methods described above for the formation and selective growth of a new solid phase in a selected fraction of a multiplicity of cells and makes it possible to maintain this new phase in the selected cells written without partial discharge in the unwritten cells: for example, we find that after application of the sensitization voltage pulse to the selected cells and then the electrolysis voltage to all the cells, maintaining of parallel coupling between cells or groups of cells by the electrical connections used to apply the electrolysis voltage does not result in partial discharge of the written cells in the unwritten cells, even when the written cells have a substantial electromotive force which one would think should force the discharge.
  • the above cells also have a second memory in coupled circuit which manifests itself after sensitization of the selected cells, that is to say after the nucleation of the new phase: we have indeed found that the electrical parallel connection of the sensitized and non-sensitized cells does not make the sensitization disappear at least for a substantial period, and does not induce parasitic sensitization of the non-sensitized cells. Still within the framework of the hypothesis formulated above on the nature of the "latent image" created by awareness, it appears that despite the infinitesimal amount of charge represented by the nuclei or germs of the new phase, these are kept despite coupling to non-sensitized cells, enough to allow further growth of the new phase when applying the electrolysis voltage. In fact, this low nucleation charge weakens over time, but it is possible to tolerate delays between the parallel connection of the cells and the application of the electrolysis voltage without lose the ability to induce growth in the new phase.
  • the growth rate of the new solid phase could be increased in a sensitized cell coupled in electrical parallel with a non-sensitized cell by applying an electrolysis voltage above the electrolysis threshold without inducing this growth in the cell not sensitized, if the electrolysis voltage is brought to its value chosen progressively along a preferably linear increasing ramp and not abruptly along a steep edge.
  • the processes discovered are particularly well characterized when the electrochemical reaction comprising the formation of a new phase is the electrocrystallization of a metal or of an alloy by cathodic reduction of ions in solution and when the electrocrystallization metal or alloy is carried out on a semiconductor electrode, in particular an electrode of tin oxide and mixed oxide of tin and indium in a transparent thin layer.
  • a semiconductor electrode in particular an electrode of tin oxide and mixed oxide of tin and indium in a transparent thin layer.
  • the new electrocrystallized phase is bismuth or a bismuth alloy.
  • the new electrocrystallized phase is copper or a copper alloy.
  • the electrolysis cells considered in the invention may exhibit losses, for example internal losses such as the backscattering of the oxidant formed at one of the electrodes to the other electrode where it can chemically reoxidize the reducing agent formed therein, for example a metal which has deposited there by electrocrystallization: in this case the writing load weakens over time; there is a progressive weakening of memory.
  • the electrolysis cells considered here in which at least one of the electrochemical reactions produced by the passage of an electric current comprises the formation of a new solid phase with a substantial overvoltage of nucleation can in particular be the elementary cells generating image points of an electrochromic or electrochemical display screen.
  • the electrolysis voltage threshold is a write voltage threshold for these cells and makes it possible to discriminate between the cells to be written and the others; that the voltage pulse greater than the electrolysis voltage threshold is a sensitization pulse which offers a second mechanism of discrimination between the cells to be written and the others, differential discrimination mechanism allowing to induce and develop levels of gray and black; that the minimum electrolysis voltage is a minimum writing voltage for an image point already sensitized; that the optical density of the written cells is maintained without discharge in the unwritten cells electrically coupled in parallel with them; that the sensitized state of the sensitized cells is maintained without causing parasitic sensitization of the non-sensitized cells electrically coupled in parallel with them and allows the selective writing of the first; and that the writing speed of the selected image points can be further increased by using writing voltages greater than the threshold applied progressively along a ramp.
  • Restandardization of the screen is carried out by short-circuiting the lines all connected in electrical parallel with the columns all connected in electrical parallel.
  • This step which is optional, but desirable in particular in the case of a rapid frequency of change of the image, consists, before resuming the sensitization procedure, of rapidly canceling all the residual charges which may still exist just after erasing, especially in unwritten cells. This is achieved by shorting the rows and columns.
  • the cell then returns to its basic internal state, a state which it presented before the implementation of the process which has just been described.
  • a faster procedure consists in combining this short-circuiting with the application between rows and columns of a lower voltage and in particular up to around half of the writing threshold.
  • the cell does not return here to its basic state but to a reference state, reproducible, other than the basic state and which has been found not to drift when the cycling of the cell is continued.
  • the electrochemical process generating optical density is the electrocrystallization of a metal or alloy by cathodic reduction of ions in solution, in particular electrocrystallization of bismuth or of a bismuth or copper alloy or of a copper alloy, on a glassy or amorphous electrode, in particular tin oxide, indium oxide, mixed oxide indium and tin.
  • the black and white points at the intersections of the columns and of the lines represent the selected and non-selected image points respectively.
  • This matrix display is constructed according to example 8 version 8.3.3 of documents FR-A-2 669 121 and US-07/910 090:
  • the following fluid formative composition is prepared: Lithium bromide 5.0 parts by weight Bismuth chloride (III) 1.4 parts by weight Copper (II) chloride 0.04 parts by weight Iron (III) chloride 0.04 parts by weight Hydrochloric acid 0.7 parts by weight Triton X 100 0.2 parts by weight Hydroxyethylcellulose "Natrosol 250 HHXR” from “Aqualon” 1.0 parts by weight Titanium dioxide “Rex” from "Titafrance” 16.0 parts by weight Water 91.0 parts by weight which corresponds to the improved material whose composition in equilibrium with an atmospheric relative humidity of 50% is: Lithium bromide 16.3 parts by weight Bismuth chloride (III) 4.6 parts by weight Copper (II) chloride 0.13 parts by weight Iron (III) chloride 0.13 parts by weight Hydrochloric acid ⁇ 0.1 parts by weight Triton X 100 0.7 parts by weight Hydroxyethylcellulose "Natrosol 250 HHXR” from “Aqualon” 3.3 parts by weight Titan
  • the ratio in this improved material between the weight of the water-soluble salts and that of water is 0.93
  • the ratio between the weight of the non-electrodepositive cation salt and that of the electrodeposible metals from an aqueous solution is 3.35
  • the halide anions represent 100% of the anions present.
  • a 6 mm diameter disc is cut from composite counter-electrodes with conductive substrate, in the form of a thin and flexible sheet, of the polyisobutylene sheet type loaded with graphite covered with a layer of graphite-based ink "Electrodag 5406 "from Acheson,
  • a layer of Demetron silver lacquer "200" is deposited on the back of each disc. These discs are then applied (with an interval between them) on the layer of improved material. Finally, connect the back of each disc to an edge of the glass plate using a self-adhesive copper tape "EZ" from Bishop resting on a self-adhesive polyester tape which isolates it from the layer of improved material. and the transparent electrode; this copper tape, which can be easily connected from the edge of the plate to an external voltage source, is electrically secured with the counter electrode using of a drop of "200" silver lacquer. Finally, a peripheral bead of silver lacquer is applied to the periphery of the transparent electrode which makes it possible to connect the transparent electrode to the external source of voltage. Neither the counter electrodes nor the connections are visible or perceptible through the opaque white layer of improved material.
  • the discs thus applied have a certain adhesion to the layer of improved material, but this adhesion is variable from one disc to another and irregular from one point to another of the same disc (which results in operation by heterogeneities of optical density). Pressure is then exerted on each disc to obtain and maintain satisfactory electrical contact.
  • a difference in potential of 1.5 Volt between each disc-shaped counter-electrode and the transparent electrode is then applied to the light-reflecting reflection cells thus formed. This latter is negatively polarized with respect to the counter-electrode. : a darkening of each cell is observed by reflection in an area exactly delimited by the projection of the disc constituting the counter-electrode.
  • the optical density is uniform within each area and can be varied according to a continuous gray scale by modulating the time according to which the current is passed. We notice that at saturation, we get a printing ink black of particularly deep tone.
  • a potential difference of opposite direction also of 1.5 Volts the optical density created is erased and the initial white appearance is restored. We observe that may extend the application of the erasing voltage beyond the total erasure without visible disadvantage.
  • the addressing diagram of FIG. 2 is applied to this matrix display, which represents, in the form of chronograms, the sequence of events of a complete cycle of writing information, maintaining said information and d erasing of said information, operating on a matrix screen of 7 lines (L1, L2, ..., L7) and 5 columns (C1, C2, ..., C5), as shown in FIG. 1.
  • the graph in FIG. 2 is an integral part of the description and illustrates the implementation of the method as described above.
  • Table 1 gives a typical list of the time and voltage values used for a matrix display device with 35 image points (7 lines and 5 columns) of 7.5 mm in a 10 mm step. It is understood that these scenarios can sometimes vary with other display devices produced with different materials and / or under different conditions, and must be readjusted experimentally.

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  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
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  • Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
EP93402488A 1992-10-09 1993-10-08 Elektrochemisches Verfahren zur selektiven Herstellung und Differentialzüchtung einer festen Phase. Anwendung an Matrixanzeigern Withdrawn EP0592327A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9212052A FR2696845B1 (fr) 1992-10-09 1992-10-09 Procédé de formation sélective et de croissance différentielle d'une nouvelle phase solide par voie électrochimique. Application aux matrices de points-image.
FR9212052 1992-10-09

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EP0592327A1 true EP0592327A1 (de) 1994-04-13

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EP93402488A Withdrawn EP0592327A1 (de) 1992-10-09 1993-10-08 Elektrochemisches Verfahren zur selektiven Herstellung und Differentialzüchtung einer festen Phase. Anwendung an Matrixanzeigern

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EP (1) EP0592327A1 (de)
CA (1) CA2108066A1 (de)
FR (1) FR2696845B1 (de)
WO (1) WO1994009476A1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003098340A1 (en) 2002-05-20 2003-11-27 Sony Corporation Display device drive method

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4175836A (en) * 1976-08-31 1979-11-27 Xerox Corporation Method and apparatus for forming visible images
EP0084603A1 (de) * 1982-01-25 1983-08-03 American Cyanamid Company Verfahren und Einrichtung zum Ansteuern einer elektrochromen Anzeigevorrichtung im Multiplexbetrieb
WO1992009004A1 (fr) * 1990-11-13 1992-05-29 Alpine Polyvision Inc. Materiau et cellule electrochromique pour la modulation de la lumiere et procede de fabrication

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4175836A (en) * 1976-08-31 1979-11-27 Xerox Corporation Method and apparatus for forming visible images
EP0084603A1 (de) * 1982-01-25 1983-08-03 American Cyanamid Company Verfahren und Einrichtung zum Ansteuern einer elektrochromen Anzeigevorrichtung im Multiplexbetrieb
WO1992009004A1 (fr) * 1990-11-13 1992-05-29 Alpine Polyvision Inc. Materiau et cellule electrochromique pour la modulation de la lumiere et procede de fabrication

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003098340A1 (en) 2002-05-20 2003-11-27 Sony Corporation Display device drive method
EP1507164A4 (de) * 2002-05-20 2008-10-01 Sony Corp Verfahren zur ansteuerung einer anzeigeeinrichtung

Also Published As

Publication number Publication date
WO1994009476A1 (fr) 1994-04-28
CA2108066A1 (fr) 1994-04-10
FR2696845A1 (fr) 1994-04-15
FR2696845B1 (fr) 1994-12-02

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