CA2108066A1 - Electrochemical process for selective formation and differential growth of a novel solid phase, and application to dots-image matrices - Google Patents

Abstract

The invention relates to a method for the selective formation and differential growth of a new solid phase in a selected fraction of the cells of a system comprising a multiplicity of electrolysis cells, in each of which one of the electrochemical reactions produced by the passage of 'an electric current in one direction implies the formation of said new phase, in which a voltage pulse called the awareness pulse above the electrolysis voltage threshold is applied to the selected cells, and subsequently the same voltage is applied electrolysis of all sensitized and non-sensitized cells; 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.

Description

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The invention relates to a training method.
selective and differential growth of a new solid phase electrochemically.

The present invention applies to a multiplicity cells in which we proceed ~ the formation and development i.e. at the growth of a phase solid electrochemically. It applies in particular to devices in which training and developing such a solid phase by way electrochemical are used to modulate a density optical by reflection or by transmission, or are combined with the formation and development of another species used for such modulation. It applies especially to devices such as display screens flat and more particularly to display devices so-called matrix screens, that is to say comprising a matrix regular of image points allowing the representation of alphanumeric characters, graphics, still images, moving images (when the renewal frequencies allow them), etc.

We know that multiple efforts have been undertaken to develop matrix flat screens of all ~: M:
sizes ranging from low information content screens to ~.
screens with very high information content for a ~:
multiple applications, such as for example 3S desktop computer screens, computer screens ~;
portable, small displays with one 21080 ~

alphanumeric character lines for calculators, translators and other pocket devices as well as for office appliances, home appliances, labels supermarket, advertising screens, big screens for large-scale representation of information from computer output, large teleconference screens, TV screens and TV ~ high definition.

The information content or ability to information representation of a display screen can be characterize as a first approximation by its number of image points ("pixels"). This is for example from the order of a thousand to a few tens of thousands for a low-end display for character representation alphanumeric, 300,000 for a computer screen in black and white and 900,000 for a color screen, from 1,500,000 for a color television screen and 4 million for a high definition television screen (TV ~ D). Each image point on a screen must be able to be addressed individually to be brought to density optical or luminance which is that of the point considered at a given time in the image represented. But with numbers of image points as indicated above for matrix screens, direct addressing, i.e.
individual direct control of each of these image points is impractical, both with regard to the manufacture of the display which would require a connecting conductor and a point-image control circuit as far as its cost. Only multiplexed addressing can be used involving a limited number of commands and connecting conductors.

The most common multiplexed addressing method of a matrix screen requires that in a matrix of mxp image points, the elementary generating cells ~. ~ The ~ '?

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of these image points are placed at the intersections of m conductive lines and p conductive columns, so that able to order them with only m + p circuits command each actuating a row or a column.

Recall that 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, both of which are transparent in a display operating by transmission. An electrical voltage or an appropriate voltage variation applied to electrodes to change the optical density of the point-image and modulate the light it reflects or transmits.
To allow matrix addressing, a matrix screen consists of a matrix of image points whose elementary generator cells are located at the intersection of two orthogonal networks of conductors electric: a network of m lines parallel to each other each of which connects all the first elementary cell electrodes located on this row, and a network of p columns parallel to each other each of which connects to each other every second elementary cell electrodes located on this column. The mxp image points are sent and ordered via m + p control circuits each activating a row or a column and it applying a particular voltage profile depending on the time. The most multiplexed matrix addressing method common is to wipe the screen line by line, applying between the line considered and each of the columns simultaneously a potential difference suitable producing the writing of the only image points selected located on this line; the sweep of the screen then starts again in the same way, either for maintain contrast, compensate for losses, etc.

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to change the image. Other methods exist, which make call for more complex application schemes of line and column tensions.

We will call selected image points, the points-image which constitute the image that we propose to represent on the screen.

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 enabling matrix addressing multiplexed or only allows it with faults (low contrast, low angle of view, crosstalk, etc.) if the electro-optical phenomenon image generator does not present not or only exhibits certain characteristics particular.

A first characteristic essential to matrix addressing is that the electro-optical phenomenon image generator (i.e. luminance generator, optical density) has a defined voltage threshold write, i.e. has a voltage threshold below which a p ~ int-image cannot be written: in the absence of such a threshold, one cannot selectively write the only selected image points of the matrix. Another necessary characteristic is that this voltage threshold writing is close to the effective writing voltage:
as via common line conductors and columns the unselected image points are found also subject to stray voltages, they can, if the threshold is too low or ill-defined, also write partially (crosstalk) and the contrast is degraded. Other features are, if not essential, at least necessary to give the image represented sufficient qualities of contrast, .

viewing angle width, etc. For example, the existence of a point-image memory makes it possible to maintain the luminance or optical density of the written picture points while scanning an image, while the absence of such a memory, they are only maintained during the addressing time of a line and the contrast found divided by the number of lines. The problems of matrix addressability have been studied and analyzed by many authors, for example Tannas (Flat Panel Displays and CRTs, Van Nostrand Reinhold Co, NY, 1985, p 106).

These necessary or desirable characteristics of the electro-optical phenomenon can exist intrinsically to various and different degrees in the various flat screen techniques and technologies: crystals liquids, plasma, thin electroluminescent layers, light emitting diodes, etc. Characteristics intrinsic often limit or penalize matrix screen applications. In the case for example nematic liquid crystals whose applications to the display are among the most important, the threshold writing is poorly defined and there is no memory;
furthermore, the need to operate between polarizer and analyzer already penalizes contrast originally and the magnitude of the viewing angle. As a result, for matrix screens using liquid crystal nematics, a mediocre contrast that degrades when the number of lines on the screen increases and the angle of vision deviates from normal.

In order to remedy a matrix addressability insufficient intrinsic nematic liquid crystals, considerable resources have been and still are devoted to develop so-called active matrices, which, associated with the matrix of image points, confer 21080fiG

indirectly to these the characteristics desired. Many variations of these active matrices exist; the most common associates with each point-image a thin film transistor (TFT) and a capacitor which act as threshold and surrogate memory and so improve contrast, speed and angle of vision of matrix screens. But the cost of the screens has active matrix is very high and it seems extremely difficult to overcome the manufacturing problem industrial with an acceptable yield of a matrix active with a percentage of faulty transistors almost zero, especially when the screen dimensions increase. Indeed, the eye only tolerates a percentage very few defective picture points. The biggest active matrix screens sold do not exceed 10 inches diagonally for application to computers and 2 5 inches for television.

Among the different modulation techniques light, electrochemical processes or electrochromics use the reversible change of color and / or optical density obtained by redox electrochemical of a so-called electrochromic material whose oxidized form and reduced form, which form a couple reversible redox, are of colors and / or densities different optics. We know a considerable number of electrochromic solids which are generally solids insoluble in the two oxidation states between which they change colors. One can quote for example among inorganic solids, WO3, MoO3, V2Os, Nb2Os, IrOx, etc.
(an extensive list is given for example in the document US-A-3,704,057j. The change of state of the solid no longer used, WO3, colorless, is its reduction to a solid blue of the form MXWO3 which is obtained by insertion electrochemical of alkaline cations, for example Li +, or of protons, in the network of WO3. Inorganic solids, 210 ~ 066 such as lutetium diphthalocyanine behave similar. Other solids, such as IrOx or Bleu de Prussia go from a colorless state to a state colored by anodic oxidation which is accompanied by the injection of protons in the lattice of the first solid and K + cations in the network of the second. A particularly class interesting are those of conductive polymers, electroactive or redox: polyaniline, polyacetyline, polypyrrole, polythioph ~ ne, etc which change state also by oxidation-reduction with insertion-desinsertion of dopants in the polymer (Kaneto et al, J.
Appl. Phys., 61 (3), 1 Feb 1987). Another class is that metal-metal ion pairs where the optical density is obtained by electrocrystallization of a metal, for example money (J. DUCHENE et al, IEEE Traductions on Electron Devices, vol RD-26, N8, August 1986, p 1263).

The basic cell of a display device electrochromic or electrochemical generally involves a transparent front electrode deposited on a plate transparent glass or plastic, on contact of which there 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., a interval filled with electrolyte, a second electrode or counter electrode (also transparent if the device works by transmission) and conductors of connection of each electrode to the control electronics outside the cell. It also has 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 couple redox can contribute in certain achievements to the chromogenic reaction that occurs ~ the electrode of work ~. For example, Habib et al. (J.App.
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Electrochemistry, 21, (1991), 203-207) describes a cell electrochromic display which presents two couples each having electrochromic properties which add up: tungsten trioxide and blue Prussia. By passing electric current through the cell in a sense (sense of writing the cell and the point-image generated by it, i.e. direction of increase optical density and / or coloring), the material electrochromic state from low optical density and / or weak coloring at a higher density state optical and / or stronger coloring. By current flow electric in the opposite direction (direction of erasure of the cell and the image point generated by it), the material electrochromic undergoes the reverse transformation.
Electrochromic modulation of the light show a set of features remarkable for many applications: low control voltage, at most a few volts, which authorizes the use of control electronics and low cost addressing; low consumption of energy; open circuit memory; interval between relatively uncritical electrode and counter electrode.
They have additional features particularly interesting for devices display: very high contrast, even in lateral vision from a high angle; excellent visibility by reflection under conditions of strong illumination such as outside in strong sunlight; gray scale extent; important temperature range of operating, often extending to low temperatures. In addition, the low energy consumption allows applications where autonomous operation (on batteries or accumulators) is required.

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But the known electrochromic processes, which periodically arouse great interest, however not given rise to industrial achievements in the area of matrix screens. Only could be considered screens accommodating direct addressing of points-image, such as seven-segment digital displays, or non-display applications such as glazing with controlled darkening. Indeed, it is not appeared possible to confer on these processes the intrinsic characteristics allowing the realization and ordering of matrix screens.

Electrochromic displays or electrochemicals have specific constraints additional regarding addressability matrix: not only should they have a threshold well-defined writing voltage, as close as possible of the actual write voltage but still the point-image should also have a circuit memory coupled (call ~ e by various authors "brief in short-circuit "), that is to say a memory under load avoiding written picture points to partially discharge in unwritten image points at which they are located necessarily electrically coupled via common row and column conductors of the matrix.
Once the voltage source has been eliminated, the written picture points have a potential difference or electromotive force not shown by the dots-unwritten image, and they tend to discharge there until balance, writing them partially while losing a part of their writing load; the picture points selected and not selected then have a neighboring optical density and the contrast becomes unacceptably low. Such a coupled circuit memory is fundamentally different from circuit memory open that almost all electrochromic displays or :
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electrochemicals possess. The absence of such a memory under load allows practically no maintenance contrast on an electrochromic matrix screen even if it there is a write voltage threshold for writing selectively the selected image points. To maintain the contrast of a matrix screen, Arellano et al (SID 78 Digest, p22) selectively discharge the image points written through the control circuits which present uen low impedance compared to those of non-image points lo written, but obviously must constantly recharge the selected picture points, at the frequency of 33Hz, which leads to considerable energy consumption electric.

No known electrochromic process presents today all of these two characteristics, in particular the second, and even the first was only obtained rarely, for example by WARSZAWSKI (document FR-A-2 669 121), Arellano (cited), Schoot et al (Appl. Phys. Letters, Vol. 23, No. 2, July 15, 1973) indicate forces that the last two authors consider as a usable threshold for matrix addressing. In in addition, the write and erase speeds of a electrochromic cells are most often slow, at least ten milliseconds for get good contrast (some processes electrochromic even requiring a few hundred milliseconds and even several seconds). The result that even if these two characteristics were obtained, writing an electrochromic matrix screen according to the conventional procedure used for matrix screens, i.e. line after line, would be very slow writing a screen would last the writing time of a cell multiplied by the number of lines on the screen; in besides it would present a characteristic aspect of "curtain" during progressive lowering. For the 210806 ~

some of the most interesting applications on the screen matrix, these speed limits (prohibiting including the representation of moving images) and appearance would be unacceptable.
Process problems and limitations electrochromic and electrochemical displays were described and analyzed by numerous authors, for example Tetsu Oi (Ann. Rev. Mater. Sci., 1986, 16, pp. 185 to 201) which concludes that intrinsic matrix addressability is prevented by the very nature of the electrochromic phenomenon.
For this author and many others, the functioning of an electrochromic matrix screen cannot be resolved only by the use of an active matrix, which would reintroduce the problems of complexity, efficiency of manufacturing and cost entrafées by the active matrices.

A first object of the present invention is, for a system comprising a multiplicity of cells electrolysis, a process of selective formation and electrochemical differential growth of a new solid phase in each cell of a fraction selected from this multiplicity of cells.

A second object is an addressing process multiplexed matrix for matrix screens electrochromic and electrochemical allowing solve the problems encountered in the prior art without use an active matrix, and allowing operate such screens with new properties of speed and contrast.

Another object of the present invention is, for a system comprising a multiplicity of cells electrolysis with electrodes coupled electrically between them by a network of conductors electric as they allow to control any what particular cell, an awareness process selective and differential cells allowing to induce electrochemically the development selective and differential ie growth selective and differential of a new solid phase in a selected configuration of cells ~ exclusion others.

Another object of the present invention is, for a system comprising a multiplicity of cells electrolysis, a differential growth process fast of a new solid phase in a configuration chosen from sensitized cells to the exclusion of others.
Another object of the present invention is, for a system comprising a multiplicity of cells electrolysis, an assisted differential holding process of the new solid phase now developed this phase in a chosen configuration of cells to exclusion of others.

Another object is an addressing process and writing an electrochemical matrix display screen or electrochromic not requiring an active matrix, involving the development of a writing threshold allowing discrimination. between image points selected and unselected image points, circuit memory coupled with written picture points avoiding the partial discharge of these in the image points unwritten and the resulting loss of contrast, as well as differential assisted maintenance of the single image points writings.

Another object is an addressing process and writing a matrix display screen 2108D ~ 6 electrochromic or electrochemical not requiring active matrix, allowing you to write the screen in one time according to an image comprising a gray scale, of keep the displayed image flicker free throughout the expected display time, and to clear the screen in one only time to change the displayed information, process allowing high image renewal frequencies authorizing their animation.

To this end, the invention provides a method of selective formation and differential growth of a new solid phase in a selected fraction of cells of a system comprising a multiplicity of electrolysis cells, in each of which one of the electrochemical reactions produced by the passage of a electric current in one direction involves training of said new phase, in which:

1) a cell is applied to the selected cells voltage pulse called awareness pulse higher than the electrolysis voltage threshold,

2) and later, the same voltage is applied electrolysis to all sensitized cells and not sensitized; the procedure allowing training and new phase growth in cells alone selected in the system and vice versa, the absence of training and development of the new phase in cells not selected in the system.
This process also has the characteristics following optionally, alone or in combination:
applies the electrolysis voltage gradually according to a preferentially linear increasing ramp; we modulate it voltage of the awareness pulse to get a differential growth of the new phase of a : i ~. . .... ..

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cell to cell; the electrochemical reaction comprising the formation of a new phase is electrocrystallization of a metal or an alloy by cathodic reduction of ions in solution; we perform electrocrystallization of the metal or alloy on a semiconductor electrode, especially an oxide electrode of tin (T0) or mixed oxide of tin and indium (IT0) in transparent thin layer; the new phase electrocrystallized is bismuth or copper or a bismuth or copper alloy.

The invention also provides an addressing method display screen multiplexed matrix electrochromic or electrochemical comprising a matrix of elementary cells generating image points placed at the intersections of two orthogonal networks of electrical conductors, characterized in that it comprises the succession of the following stages:

1) we proceed by passing the current in the direction writing an image point, developing a electrochemical reaction involving the formation of a new solid phase, the formation and growth of a such solid phase being used to modulate the density optical by reflection or transmission or are combined with the formation and growth of another species used for such modulation;

2) we carry out the sequence of the phases of a cycle complete writing an image, maintaining said image displayed and erasing said image by the succession of the following phases:

a) multiplexed awareness phase of the screen - we address the lines one after the other the other ; ~;

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- While this line is addressed, we apply a voltage pulse called awareness between said line and the columns defining at the intersection with said line the image points of said image, we applies to the other columns with respect to said line a voltage below the writing threshold, preferably a zero voltage or the open circuiting of said columns;
- we then do the same with the following line and so on until the last line;

we thus form on the whole screen an "image latent "in a time equal to the duration of the pulse awareness multiplied by the number of lines;

b) image writing phase we "rev ~ the" latent "image by applying a write voltage between the lines all connected in electrical parallel and the columns all connected in electric parallel until the desired contrast is obtained compared to the rest of the screen;

c) image maintenance phase we maintain the written image for the duration display;

d) image erasure phase we erase the written image by applying a tension and / or by making a short circuit between the lines all connected in electrical parallel and the columns all connected in electrical parallel;

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e) possible phase of restandardization of the screen we realize the restandardization of the screen in shorting the lines all connected in electrical parallel with the columns all connected in electric parallel.

According to other features of the invention which result from the following, these methods also exhibit the following features, optionally, alone or in combination: 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 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 an electrode glassy or amorphous including tin oxide (T0), oxide indium, mixed indium tin oxide (IT0); we modulates the voltage of the awareness pulse of a point-image according to the level of gray or black that must to present the point-image considered; we choose couples redox involved in the electrochemical reactions of cells so as to present a difference from their redox potentials, so the cells have a electromotive force when the image points they generate are written; we compensate for any weakening of the writing load of the image points written during the information display period by application between lines all connected in parallel electric and the columns all connected in parallel electric, or voltage pulses controlled by the difference between the voltage between the two networks of electrical conductors and a reference voltage, i.e.
of a direct voltage equal to a reference voltage, the 210 ~ 066 reference voltage ~ rence being equal to the electromotive force cells written before any loss; we maintain -the image written during the display period, either by its intrinsic memory, either by applying between columns all connected in electrical parallel and lines all connected in electrical parallel with pulses of voltage controlled by the di ~ ference between the voltage measured between rows and columns and a voltage of reference corresponding to the black of the image; we distribute the voltage of the awareness pulse into a component row Vline and a column component VcOl with respect to the voltage of the already addressed lines taken as reference, such that Vligne and VcOl are each below the write threshold while the sum Vline +
VcOl is greater than this threshold and in that we apply a voltage VcOl at the selected columns and a voltage null for unselected columns.

In the present invention, the expressions "a new solid phase "and" one of the reactions were used, but the invention also includes the case where several new phases ~::
solids are formed simultaneously and the case where both electrochemical conjugate reactions are concerned during the passage of electric current in one of the two directions. : ~

The other characteristics of the invention will be well understood thanks to the description which follows in ~:
reference to the accompanying drawings in which::
/
~ / Figure 1 is a particular example of a schematic representation of an electrochemical screen or multiplexed matrix electrochromic with 35 image points (7 ~: ~
rows and 5 columns) according to the invention;
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- Figure 2 which shows an example of a diagram of multiplexed matrix addressing of an electrochemical screen or electrochromic with 35 image points (7 lines and 5 columns) according to the invention in the form of a chronogram.

Definitions are agreed in the text following:

- "Cell or electrochemical cell or cell electrolysis ": an elementary electrochemical device with two electronically conductive electrodes separated by at least one electrolyte, in which the passage of electric current in one direction develops electrochemical reactions combined with interfaces electrode-electrolyte and passing in the opposite direction develops reverse conjugate reactions; .

- "Electrolysis": the development of reactions electrochemical in the sense involving training and:
growth of the new solid phase;
.
- "New solid phase": a solid phase which did not exist at an earlier stage, before the passage of electric current in one direction, including a phase having crystallographic characteristics or morphological or composition at least partially different from those of the phases that existed before the passage of electric current in said direction, and which form and develop (grow in mass and volume) by passage of electric current in said direction;

- "Written cell": an electrolysis cell in which a new solid phase has been by way electrochemical formed and developed in mass and volume up to the equivalent of a given electrical charge that 210806 ~
. 19 will call write load; per unwritten cell one cell o ~ the new solid phase has not been formed;

- "Electrolysis voltage": a voltage allowing development of electrochemical reactions including growth of the new solid phase, this one already being formed;

- "Minimum electrolysis voltage": the voltage minimum required for reaction development electrochemicals including the growth of new phase, this being already formed;

- "Electromotive force rf.em) of the cell written ": the voltage presented by the cell after removal the electrolysis voltage source; we note that in the case where ~ the electrochemical reactions involved are thermodynamically reversible once the new phase formed, the value of the electromotive force is equal to the minimum electrolysis voltage once the new phase formed; it is smaller if one and / or the other of the electrochemical reactions is thermodynamically irreversible;

- "Electrolysis voltage threshold": the voltage minimum required for reaction development electrochemicals including the formation of the new phase from a state where it did not yet exist;

- "Write voltage threshold": the threshold of electrolysis voltage when the cell is generating of an image point in a display screen electrochromic;

- "Nucleation of ~ a new phase ~: training initial nucleus or germ of this new phase, whatever the mechanism of this training and the structure, texture and location of these nuclei or germs, since these nuclei or germs are likely to growth by passing electric current in the direction having given rise to the formation of these nuclei or germs;

- "Overvoltage in nucleation of a new phase":
the overvoltage required by electrochemical nucleation of this new phase; the invention is particularly suitable in the case where the nucleation overvoltage is:
substantial or significant as shown for example of documents: Industrial Electrochemistry, Derek Fletcher, 1982, Chapman, NY, and Modern Aspects o ~
Electrochemistry, vol.3, BOCKRIS and CONWAY;
:
- "Awareness impulse ~ ': an impulse of voltage above the electrolysis voltage threshold, capable of inducing the growth of a new phase by application of an electrolysis voltage;
- "Sensitized cell": a cell to which been.applied an awareness boost;

- "Nemoire in coupled circuit": 1) conservation of the electrical charge of one (or more) cell (s) written when it is (are) linked in electrical parallel with one (or more) non-cell (s) written (s) directly or through two networks of electrical conductors such as those of a screen matrix, 2) conservation of the awareness of a (or more) cell (s) sensitized when that (s) -this is (are) coupled in electrical parallel with a (or more) cell (s) not directly sensitized or through two conductor networks electrical such as those of a matrix screen;

- "Differential growth": the growth of a new phase according to a structure, texture, morphology, etc, different from one electrolysis cell to another.

The present invention applies to a cell of electrolysis and a multiplicity of cells electrolysis on at least one electrode of each of which the electrochemical reaction involves the formation and growth of at least one new phase solid when the electric current flows in one direction (and resorption of this new phase when the current electric goes in the opposite direction). It applies in particular to an electrochemical cell and a multiplicity of electrochemical cells in which one conducts electrocrystallization of a metal or alloy metallic or solid composition by reduction cathodic, or the formation of an oxide or another metallic compound by anodic oxidation, or insertion or intercalation or disinsertion or deintercalation of an ion in the network of a compound metallic or electroactive polymer. It applies in particular to the electrochemical cells constituting the cells generating image points of the devices so-called electrochromic displays in which the generation of the optical density of the image point is carried out by electrocrystallization of a metal, metallic alloy or solid composition such as diheptyl-violog ~ ne, electrocrystallization of a metal or other oxide metallic compound, insertion or doping or disinsertion 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. It also applies ~ cells in which the generation of the optical density of the point-image is accompanied by electrochemical reactions such as the previous ones occurring on the second electrode without it necessarily participating in the 210 ~ 06 ~

generation of optical density: this is the case for example cells operating by reflection in which the two electrodes are separated ~ es by an opaque material, by example a white reflector or reflective pigment opaque. It applies in particular to cells and flat panel display devices described in patent applications n FR-2,618,566, n ~ FR-2,618,567, n FR-2,669,121 in which the increase in density optics is obtained by cathodic reduction of ions in solution in an electrolyte consisting of a solution aqueous gelled in a metal or alloy which electrocrystallizes on a transparent electrode, and the decrease in optical density is obtained by the reaction reverse electrochemical: anodic oxidation of this metal or ion alloy in solution.

We know that many reactions electrochemicals involve the formation of a new phase from a different pre-existing phase. This new phase can be a metal or alloy resulting from cathodic reduction of an ion in solution, an oxide resulting from the anodic oxidation of a species dissolved in solution (e.g. PbO2 from a solution of nitrate), a metal salt resulting from the oxidation of a metal (for example PbSO4 formed from lead during the discharge of a lead-acid battery), a metal salt resulting from the reduction of another oxide (e.g.
PbSO4 formed by reduction of PbO2 from the electrode positive when discharging a lead-acid battery), or a gas (e.g. chlorine in an electrolyser chlorine-alkali), or of LixWo3 solid obtained by electrochemical intercalation of Li + ions in the network of WO3 tungsten trioxide, or doped polythiophane by electrochemical injection of a dopant into the polymer undoped.

210 ~ 3066 Such reactions involving the formation of a new solid phase frequently exhibit unique feature: current features-tension before and after the formation of the new phase are different: it is for example well known that the current-voltage characteristic (polarization curve) of of copper cathode pot from an ion solution copper on an inert graphite electrode is notably different from that of the same ~ electrochemical action if the graphite electrode is already covered with a thin copper layer. This situation results from the fact that the formation of a new phase requires nucleation of germs of this new phase, process thermodynamically irreversible which requires energy substantial additional activation to occur, that is, a substantial overvoltage. Once these germs or nuclei formed, their growth can continue without requiring this overvoltage.
.
Even when the electrochemical reaction involving transforming a phase into a new one is thermodynamically reversible, this initial formation of the new phase, creation of germs or nuclei, cannot occur without an activation energy which translates by a temporary overvoltage. Generally, this is the creation of nuclei, germs or crystallites of the new phase. But whatever the mechanism, we observe electrochemically, an initiation overvoltage of the new phase. This overvoltage is temporary, since once the new phase is initiated, the pursuit of its growth is done by enlargement of the nuclei or germs created by a mechanism that no longer requires this original surge, especially because this growth continues in epitaxial relation with the phase already present, or, if it is not an epitaxial relationship true, with reduced or minimal distortion of the 21080 ~ 6 network. The electrolysis can therefore continue with a voltage as low as the minimum electrolysis voltage.

Various mechanisms and many factors S intervene in this activation energy required by the nucleation of the new phase. In the case of a new solid phase, an important role is played by the relationship between its crystalIine structure, etc., and that of the conductor electronic on which or in which it is formed. The initial formation of nuclei or germs of this new phase takes place on or inside another phase with electronic conductivity: this other phase is usually an electrode that does not participate in electrochemical reaction (e.g. tin oxide or mixed tin and indium oxide used as transparent electrode in flat screens); she can also be the solid phase from and in which develops the new phase (solid conductors electronics such as tunqstene trioxide or electroactive polymers such as polythiophene, polyaniline, polyacetylene, which change state oxidation 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 morphology different from that on the surface or at inside of which it grows. Its nucleation does can therefore generally not be carried out in relation epitaxial with this support or in continuity with the network from which it develops. It therefore requires that the first germs are formed with a distortion of their network, i.e. at a higher energy level than the normal network; providing this energy additional during the electrochemical reaction is expressed by an overvoltage. As the germs develop, the network is less and less 210806 ~

distorted, and growth continues without requiring this overvoltage. The greater the difference between crystal structures and more generally morphologies of the new phase in formation and of the support phase, and the higher the overvoltage of nucleation high. The real situation is actually more complex and factors influencing energy and therefore the more nucleation overvoltages; for example, a very important role is played by surface defects and the various texture singularities of the support phase which can behave like privileged places of nucleation ; moreover, certain formed nuclei can not develop during the passage of electric current.

Electrolysis during which at least one of two electrochemical reactions involved involves the formation of a new phase, including a new solid phase, can only start to occur if the applied voltage is temporarily above a threshold.
This electrolysis voltage threshold is at least equal to the sum of the minimum electrolysis voltage and the overvoltage of nucleation of the new one (s) phase (s). This threshold may be higher, others momentary thermodynamic irreversibilities the nucleation of the new phase can affect the progress of one and / or the other of the two electrochemical reactions. Once nucleation of the new phase obtained, electrolysis can occur continue with a voltage lower than the threshold, which can be as low as the minimum voltage electrolysis.

We first found that in a system comprising a multiplicity of electrolysis cells in which at least one of the electrochemical reactions produced by electrical current includes training 2iO306 ~

, of a new solid phase, with an overvoltage substantial nucleation one can use existence of this nucleation overvoltage of the new phase for the selective formation of said new phase in each cell only of a selected fraction of cells of the system, so as not to cause the growth of this new phase only in the selected cells only.
According to the invention, a voltage is applied for this purpose.
above the cell electrolysis threshold selected, and an electrolysis voltage lower than threshold for electrolysis of unselected cells:
then observe in the only selected cells the formation and growth of the new phase.

According to the invention, a method has been found for selective formation and differential growth of a new solid phase in a selected fraction of cells of a system comprising a multiplicity of electrolysis cells, in each of which one of the electrochemical reactions produced by the passage of a electric current in one direction involves training of said new phase, in which:

1; we apply to the selected cells a voltage pulse called awareness pulse higher than the electrolysis voltage threshold, 2) and later, the same voltage is applied electrolysis to all sensitized cells and not sensitized.

The process for training and growth of the new phase in the selected cells only in the system and vice versa, the lack of training and of development of the new phase in non-cells selected in the system.

21 ~ 06 ~

So in a system with a multiplicity electrolysis cells in which at least one of electrochemical reactions produced by the passage of a electric current includes the formation of a new solid phase with a substantial overvoltage of nucleation, it is possible, according to the invention, to use the temporary nature of this nucleation overvoltage for obtain selective formation and growth of said new phase in each cell only a fraction selected from system cells, although applying the same electrolysis voltage to all cells in the system simultaneously. To this end, we first apply a voltage pulse above the electrolysis threshold at only selected cells, then we apply to all cells an electrolysis voltage below the threshold electrolysis: we then observe in the cells only selected the formation and growth of the new phase. Depending on the size of the cell, its structure and composition, and the nature of the electrochemical reactions involved, the necessary duration of the pulse for generating awareness can vary by a few microseconds, or even less, to several milliseconds.

It has thus been found, according to the invention, that a electrolysis voltage applied simultaneously to sensitized cells and non-sensitized cells selectively develops the new phase in raw. Everything happens as if the impulse of sensitization sensitized cells so that allow further selective development of the new phase. To fully understand the invention, one can draw a parallel with the photographic processes in which awareness of a photographic photograph by short-term illumination allows development subsequent selection of the silver image in the regions 210 ~ 06 ~

illuminated. The awareness boost created in cells a "developable" electrochemical "latent image"
by electrolysis, to compare with the latent image created in a photographic photograph by illumination and developable chemically by a reducer. This "latent image"
electrochemical is in all likelihood constituted by nuclei or germs of the new solid phase nucleated by the awareness pulse, the invention however, is not related to this assumption.
Throughout this text, the expressions "latent image"
and "revelation" are used with reference to photographic processes and this in order to do well understand the present invention. However, it must be understood that the method according to the invention is completely different from the photographic processes in which there are constitution of a latent image then revelation.

According to the invention, it has also been found that could modulate the pulse voltage of awareness to achieve differential growth of the new phase from one cell to another. The above awareness is to be reconciled there again for good understand the invention is only for this reason, like latent in photography: everything happens as if the number of developable nuclei or germs created by the pulse of awareness was a function of the tension of this impulse, just as in photography it is function of the illumination. Indeed, by applying to cells that have been sensitized with different voltages the same electrolysis voltage during the same period, we observe a growth differential of the new phase: the morphology of the new phase appears different from cell to cell.
It was therefore found that the method according to the invention allowed for differential awareness by differential growth.

We were also surprised to find that electrolysis cells in which at least one of electrochemical reactions produced by the passage of a electric current includes the formation of a new solid phase with a substantial overvoltage of nucleation once presented a memory in coupled circuit. This coupled circuit memory is develops during the implementation of the processes described higher training and selective growth of a new solid phase in a selected fraction of a multiplicity of cells and helps maintain this new phase in selected cells written without partial discharge in unwritten cells: by example, we find that after applying the voltage of sensitization to the selected cells then of electrolysis voltage to all cells, the maintaining a parallel coupling between the cells or groups of cells by electrical connections having been used to apply the electrolysis voltage not entered ~ do not the partial discharge of the cells written in them unwritten cells, even when written cells have a substantial electromotive force which is might think she should force the discharge.

We found even more surprisingly that the above cells also have a second coupled circuit memory that manifests after sensitization of selected cells, i.e.
after nucleation of the new phase: we found in effect that the electrical parallel connection of cells sensitized and not sensitized does not disappear ~ tre awareness at least for a period substantial, and does not induce parasitic sensitization 210806 ~

non-sensitized cells. Still in the context of the hypothesis formulated above on the nature of "the image latent "created by awareness, it appears that despite the infinitesimal amount of charge represented by the nuclei or germs of the new phase, these are retained despite coupling to non-cells sensitized, enough to allow later the growth of the new phase when applying the electrolysis voltage. In fact, this low charge of nucleation weakens over time, but we can tolerate delays between the parallel connection of cells and applying electrolysis voltage without lose the ability to induce new growth phase.
We can formulate the following hypothesis (at the validity of which the invention is not linked) with regard to concerns the memory mechanism in coupled circuit written cells: so that a written cell can be unload in an unwritten cell connected to it electric parallel, it should be able to nucleate this new phase; that would require her has a voltage above the voltage threshold electrolysis, and which is at least the sum of the voltage minimum electrolysis and nucleation overvoltage of the new solid phase. The voltage or fem generated by a written cell is at most equal to the voltage minimum electrolysis (in case the reactions electrochemicals involved are thermodynamically reversible, and it is lower in case irreversibility). It is therefore lower than the voltage that would be required at least the value of the overvoltage nucleation of the new phase. The written cells do not therefore cannot induce nucleation of the new phase solid in the unwritten cells to which they are coupled in parallel and therefore cannot be unloaded there ~ -210806 ~

partially. We could not find a hypothesis satisfactory with regard to circuit memory coupled sensitized cells.

We still found with surprise that we could increase the growth speed of the new phase solid in a sensitized cell coupled in parallel electric with a cell not sensitized by applying an electrolysis voltage above the electrolysis threshold without inducing this growth in the cell not sensitized, if the electrolysis voltage is brought up to its value gradually chosen according to a ramp preferentially increasing linen ~ area and not abruptly on a stiff front.
lS
We still found that the processes discovered were 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 of the metal or alloy takes place on a semiconductor electrode, in particular a tin oxide and mixed tin oxide electrode and indium in transparent thin layer. We have for example observed that in a point-image generating cell in which the optical density is created by a metal or alloy having thus electrocrystallized, the optical density obtained by the passage of the same electrical charge during electrolysis was an increasing function of height of the awareness voltage boost beforehand applied. This is how by increasing the tension of awareness, we gradually go from a light gray to a dense black.

According to a first preferred variant of the invention, the new electrocrystallized phase is of the bismuth or a bismuth alloy.

According to a second preferred variant of the invention, the new electrocrystallized phase is of the copper or a copper alloy.

The electrolysis cells considered in the invention may present losses, for example internal losses such as backscattering of the oxidant formed at one of the electrodes towards the other electrode where it can chemically oxidize the reducing agent formed therein, for example a metal which is deposited there by electrocrystallization: in this case the writing charge weakens over time; there is weakening progressive memory. We have found according to the invention that in the particular case of electrolysis cells whose electromotive force is a function of the charge of writing, which is for example the case of cells according to FR-A-2 618 566 and FR-A-2 669 121, when a cell written is coupled in electrical parallel to a cell unwritten one could selectively maintain the write load of cells written by maintaining the electromotive force of the cell written to the value corresponding by pulsed application of voltage to the set of the two cells: so surprisingly, the writing load of the written cell is thus found maintained without the unwritten cell is written. Everything happens as if the written cell had a lower impedance than the non-cell written. We call this process according to the invention of compensation for losses and maintenance of the write status cells written using an external source of voltage applied both to written cells and not , _ written of a multiplicity ~ of cells: assisted memory differential.

The electrolysis cells considered here in which at least one of the electrochemical reactions produced by the passage of an electric current includes the formation of a new solid phase with a substantial nucleation overvoltage can particular being the cells, elementary generators of image points of an electrochromic display screen or electrochemical. It is found according to the invention in particular that the electrolysis voltage threshold is a voltage threshold of writing for these cells and allows to discriminate between cells to be written and others; than the voltage pulse above the voltage threshold electrolysis is an awareness boost that offers a second mechanism of discrimination between cells to be written and the others, mechanism of differential discrimination allowing to induce and develop grayscale and black; that the tension minimum electrolysis is a minimum write voltage for an image point already sensitized; that the density optics of written cells is maintained without discharge in unwritten cells electrically coupled in parallel with them; that the sensitized state of the cells sensitized is maintained without causing the parasitic sensitization of non-sensitized cells electrically coupled in parallel with them and allows selective writing of the former; and that speed writing the selected image points may still be increased by using write voltages higher than threshold applied progressively along a ramp.

As an example of implementation of the invention, we built cells 3 millimeters in diameter according to example 8 version 8.3.3 described in the documents 2 ~ 080 ~

FR-A-2 669 121 and Us-o7 / 9lb 090. In these cells, the passage of current in the direction of writing produced by cathodic reduction of Bi (III) ions dissolved in a gelled aqueous solution electrocrystallization of bismuth on a tin oxide or mixed oxide electrode indium and tin, and the conjugate oxidation of the ion bromide to bromine at the counter electrode. We proceed with these cells in the following tests:

1) We write one of these cells with a voltage of 1.2 Volts until the original white changes to black;
this cell, which has an electromotive force of 0.82 Volt generated by the bismuth-bromine couple that has been there developed by the passage of the electrolysis current ~ current write), is connected in parallel to a cell not written: no transfer of optical density from the first cell to the second does happen.
-:
2) A pulse is applied to one of these cells voltage of 1.5 Volts with a duration of 1 millisecond, then we connect it in electrical parallel to another cell having not undergone this impulse; we then apply to the whole for a period of one second a voltage write voltage of 0.9 Volt: we observe that the optical density of the sensitized cell increases while that of the other remains unchanged (white appearance); we can note that after sensitization, no change in density optics are not perceptible on the sensitized cell;
after removal of the electrolysis voltage source, and although the written cell then presents a force 0.78 Volt electromotive, it does not undergo any discharge even partial in the unwritten cell which would transfer part of its optical density.

3) a pulse is applied to one of these cells voltage of 1.5 Volts with a duration of 1 millisecond, we 2: 10806 ~

connects it in electrical parallel to another cell not having undergone this impulse, then we apply to the whole a writing tension that is made to grow linearly from 0 to 1.4 Volts for 50 milliseconds (according to the ramp already mentioned) and which is then kept at 1.4 Volts for 300 milliseconds: the cell sensitized blackens while the non-sensitized cell stays white.

4) We apply to a cell a pulse of sensitization lasting 1 millisecond by varying the voltage from one test to another of a series of tests in a interval from 1 Volt to 1.8 Volts, voltage and time of writing being the same as in (3): we obtain optical densities which are placed on a gray scale.

A mode of implementing the invention particularly important for its applications of the invention is a rapid matrix addressing process multiplexed with a matrix display screen electrochromic or electrochemical formed of a matrix of mp cells placed at the intersections of two networks orthogonal of electrical conductors, m lines and p columns. This process, which allows frequencies to be reached notable screen image renewal features the succession of the following stages:

1) - we proceed by passing the electric current in the direction of writing an image point, developing an electrochemical reaction involving the formation of a new solid phase, training and growth of such a solid phase being used to modulate the optical density by reflection or transmission or are combined with the formation and growth of another species used for such modulation;

2) the sequence of the phases of a cycle is carried out complete writing an image, maintaining said image displayed and erasing said image by the succession of the following phases:

a) multiplexed awareness phase of the screen - we address the lines one after the other the other ;

10- while this line is addressed, we apply a voltage pulse called awareness between said line and the columns defining ~ the intersection with said line the image points of said image, we applies to the other columns with respect to said line a voltage below the write threshold, preferably a zero voltage or the open circuiting of said columns; the tension of the awareness pulse of an image point is modulated according to the gray level or black that the image point in question must present.
- we then do the same with the following line and so on until the last line.

we thus form on the whole screen an "image latent "in a time equal to the duration of the pulse awareness multiplied by the number of lines.
~. ~
b) image writing phase:
we "reveal""the latent image" by applying a 30 write voltage between the lines all connected in electrical parallel and the columns all connected in electric parallel until the desired contrast is obtained compared to the rest of the screen. . : ~

35 Sensitized image points blacken simultaneously and reach the gray or black level 21080 ~

corresponding to their level of awareness; the non-sensitized image points do not appear. We "revals" thus the "latent" image in a time equal to that necessary to write a single image point.

c) image maintenance phase we maintain the written image for the duration display. As long as the information displayed should not be changed, it can be maintained without weakening by the intrinsic memory of cells. However, if he there is any cause of pressure drop which too quickly weaken the contrast, we can, in the special case where the cell has a force electromotive which is a function of the writing load, keep the image as it is at the optical density level achieved by offsetting internal losses through the differential assisted maintenance procedure: we apply between the lines all connected ~ es in parallel ~ the electric and the columns all connected in electrical parallel voltage pulses whose delivery is controlled by the difference in voltage read between the two conductors and a reference voltage equal i ~ this voltage (or fem) when the optical density (or the image contrast) is the one we have before any loss;
when this difference is canceled or reversed the voltage pulses stop, and they resume when the gap manifests again. Only the image points writings have their losses compensated; the image points no writings undergo no change in optical density from the share of these sustaining impulses although they are also submitted. The image is preserved without flicker as long as you want to maintain it.
A variant of this assisted maintenance procedure differential is to apply between rows and columns not voltage pulses, but a permanent voltage equal to the fem before any loss.

'"'''''':':'~' ~. ''! ,,,"~;;,,, j, i.

21080 ~

According to the invention, the written image is maintained during the display time either by its memory intrinsic, either by applying between the columns all connected in electrical parallel and the lines all connected in electrical parallel pulses of voltage controlled by the difference between the voltage measured between rows and columns and a voltage of reference corresponding to the black of the image.
.
According to the invention, any weakening is compensated for of the writing load of the image points written during the information display period by application between lines all connected in parallel electrical and the columns all connected in parallel ~;
electric, or voltage pulses controlled by the difference between the voltage between the two networks of - ~
electrical conductors and a reference voltage, i.e.
of a direct voltage equal to a reference voltage, the reference voltage being equal to the electromotive force cells written before any loss.

d) image erasure phase we erase the written image by applying a tension and / or by making a short circuit between the lines all connected in electrical parallel and the columns all connected in electrical parallel. -The written image points are erased simultaneously;
unwritten image points, which also undergo erase voltage, are not affected. So we erase the entire screen image in a time equal to that necessary to delete a single image point.

21080 ~

e ~ possible screen restandardization phase We realize the restandardization of the screen in shorting the lines all connected in electrical parallel with the columns all connected in electric parallel.

This step, which is optional, but desirable especially in the case of a rapid frequency of change of the image, consists, before resuming the procedure of awareness, to quickly cancel all charges residuals that may still exist right after erasure, especially in unwritten cells. That is obtained by short-circuiting the lines and columns. The cell then returns to its internal state of base, state it presented before the implementation of the process which has just been described. Faster procedure is to combine this short circuit with the application between lines and columns of a voltage lower and in particular being able to go up to approximately the half the write threshold. The cell does not come back here to its basic state but at a reference state, reproducible, other than the basic condition and which has been observed do not drift when continuing the cell cycling.

For a change of the displayed image, you can then repeat the procedure at the first step.

According to a preferred embodiment of the invention, the process electrochemical optical density generator is electrocrystallization of a metal or alloy by cathodic reduction of ions in solution, in particular electrocrystallization of bismuth or an alloy of bismuth or copper or a copper alloy, on a glassy or amorphous electrode, in particular tin oxide, indium oxide, mixed oxide of indium and tin.
... .

2i08066 This preferred method of multiplexed matrix addressing an array of electrochromic cells or:.
electrochemical according to the invention present in combination: -the following features ~
-- "Latent image" is generally not noticeable by the observer, due to the tenuous nature of the micro-charge involved;

10- The total writing time of a screen is defined by the sum of the duration of the awareness pulse multiplied by the number of lines, and the duration - ~
writing a single image point, whatever the ~;
number of screen lines;
. .
- Screen writing is done one image at a time applying to all image points without discrimination the same voltage during the same time and not line by line ;
- It is the same for assisted maintenance is carried out using a potential difference ~ - ~
applied globally to all columns compared to all lines, regardless of:
25 real distribution of written and unwritten image points. ::
on the screen ; it should be noted that this memory process assisted differential, which acts on all image points connected in electrical parallel, maintains uniformity of appearance and compensates for any defects in 30 manufacturing which could result in a defect in certain image points from the point of view of memory intrinsic.

- The same is true for erasing the screen:
35 it is performed globally for the entire screen at once without discrimination between written image points and others :::
~ "

; so it does take, regardless of the screen size, than the time required to erase a single image point;
it is the same for the restandardization of the screen.
- The contrast is the same as that would get direct addressing, and it's independent of number of lines.

One of the significant consequences of these characteristics is the possibility of reaching image renewal frequencies allowing animation of these.

The invention is now described with the aid of a nonlimiting example referring to Figures 1 and 2 attached.

We build a matrix display of 35 points-image (7 lines (L1, L2, ......., L7) and 5 columns (Cl, C2, ..., C5)) of 7.5 mm in a 10 mm pitch such that shown schematically in Figure 1.

In this figure 1, the black and white dots at intersections of columns and rows represent respectively the image points selected and not selected.

This matrix display is built according to Example 8 version 8.3.3 of documents FR-A-2 669 121 and;:
US-07/910 090::

Preparing the fluid formative composition next :
Lithium bromide 5.0 parts by weight ~ .. -Bi chloride ~ muthtIII) 1.4 ""

2108 ~ 6 ~ -.

Chloride dQ copper ~ II) 0.04 "n ~.
Iron (III) chloride 0.04 nn Hydrochloric acid 0.7 n Triton X 100 0.2 n Hydroxyethylcellulo3e "Natrosol 250 HHXR "from" Aqualon "1.0""
"Rex" titanium dioxide "Titafrance ~ '16.0""
Water 91.0 n 1 0: '' which corresponds to the improved material including the ~: composition in equilibrium with relative humidity 50% atmospheric is:

Lithium bromide 16.3 parts ~ by weight: -Bi ~ muth (III) chloride 4,6 Copper chloride ~ II) 0.13 n Iron (III) chloride 0.13 ~ "
Hydrochloric acid <0.1 1 '"::
Triton X 100 0.7 Hydroxyethylcellulo ~ e "Natro ~ ol 250 HHXR "from" Aqualon "3.3 n "Rex" titanium dioxide ~ Titafrance "52.1 n -Water. 22.7 ~ n The ratio in this improved material between the weight water-soluble salts and that of water is 0.93, the ratio of the weight of the cation salt not electrodepositable and that of electrodepositable metals from an aqueous solution is 3.3S, and the anions halide ~ nure represent 100% of the anions present. ~:
Apply using a helical wire rod ~ dal successive layers, followed by drying, fluid formative composition on the transparent electrode a glass plate covered with an "ITO" electrode ; ~ `~ ''' -~

210806 ~

until a layer of the improved material is obtained corresponding to a total thickness of about forty microns covering the entire transparent electrode ~ except for a peripheral band; this layer is white and opaque.

A 6 mm diameter disc is cut from composite counter electrodes with conductive substrate, thin and flexible sheet shape, of the sheet type polyisobutylene loaded with graphite covered with a layer "Electrodag 5406" graphite ink from Acheson, A layer is deposited on the back of each disc "200" silver lacquer from Demetron. These discs are then applied (with an interval between them) on the layer of improved material. Finally, we connect the back of each disc at one edge of the glass plate using a ribbon sticker "EZ" copper sticker resting on a ribbon polyester sticker that insulates it from the layer of improved material and transparent electrode; this ribbon copper, which can be easily connected from the edge from the plate to an external voltage source, is electrically secured with the counter-electrode using of a drop of "200" silver lacquer. Finally, we apply a bead on the periphery of the transparent electrode silver lacquer device that connects the electrode transparent to the external voltage source.
Neither the counter electrodes nor the connections are visible or noticeable through the opaque white layer of improved material.
~, ..: ' The discs thus applied have a certain adhesion to the improved material layer but this adhesion is variable from one disc to another and irregular from one point to another on the same disc (which translates in operation by density heterogeneities 210806 ~
~ - 44 optical). We then put pressure on each disc to obtain and maintain electrical contact satisfactory.

We then apply to the modulation cells of the light by reflection so made up a difference of 1.5 Volt potential between each counter electrode in disc shape and the transparent electrode, the latter being negatively polarized with respect to the electrode: a blackening of each cell according to an area exactly delimited by the projection of the disc constituting the counter-electrode. The uniform optical density within each area and we can vary it on a continuous scale of gray by modulating the time according to which we pass the current. We notice that at saturation, we get a black particularly deep tone printing ink.
By applying a potential difference of opposite direction also 1.5 Volts, the optical density created is erased and we restore the initial white aspect. We observe that may prolong the application of the erase voltage to the beyond the total erasure without visible disadvantage.
.
We apply to this matrix display, the diagram Addressing Figure 2 which represents, in the form of chronograms, the sequence of events of a complete cycle writing information, maintaining said information and erasure of said information, operating on a matrix screen of 7 lines (Ll, L2, ..., L7) and 5 columns (Cl, C2, ..., C5), as represented by Figure 1.

The graph in Figure 2 is an integral part of the description and illustrates the implementation of the process such as described above.

Y'- ',''''~'',''``','''', ,, ~:

21080 ~

These chronograms represent graphically, for each row and each column, the voltage values (V) (ordinate axis) during the different phases a full cycle:

- A: awareness;
- B: ~ writing;
- C: maintenance;
- D: erasure;
- E: short circuit, successive in time (T) (x-axis).

The parameters of the timing diagram in Figure 2 are defined as follows:
. .
- Tp: duration of a micro- cycle processor .
...
- Ti: width of the pulse sensitization ~ Tw: writing time ~ TSR duration of the increasing ramp of:;.
line component of write voltage. ~
~ .... ..
~ TSC: duration of the increasing ramp of the column component of the voltage writing;

- TE: erasure time ~ TCC: duration of the short circuit 2 ~ 080 ~ S

- Vp: prepolarization voltage of a line ~ VI: line component of the implusion of sensitization ~ VL: column component of the pulse awareness - Vx: potential of the line after sensitization.

- Vw: line component of the voltage writing ~ VLl: column component of the origin of the write voltage ~ VL2: column component of the voltage writing ~ VM: column component of the voltage holding reference ~ VE: line component of the voltage the column component - being zero we found according to the invention that we could starting again the tension of the awareness pulse in a row component Vline and a column component VcOl compared to the voltage of the already addressed lines taken as a reference, such that Vligne and VcOl are each below the write threshold while the sum Vli ~ ne +
VcOl is greater than this threshold and in that we apply a ~ "~;"' 2108 ~

voltage VcOl at the selected columns and a voltage null for unselected columns.

Table 1 gives a typical list of values for time and voltage used for a device matrix display at 35 image points (7 lines and 5 columns) of 7.5 mm in steps of 10 mm. We understand that these cases can sometimes vary with others display devices made with materials different and / or under different conditions, and must be readjusted experimentally.

, 210 ~ 061 ~
48 ' ~ A ~ L ~ A ~

T ~ N ~ ION (on 3 ~ yolts):
.
VI- ~ - 600 VM: ~ 350 VW: 1,700 FR ~ ~ 1,500 VI ~ ~ 700 Vx '~ ~ 35 VLl ~ ~ ' vL2: - 5 ~ 5 TE ~ P ~:
DURATION 1) ~; LA Rl ~ NE ~ E DP ~
; ~ 5 ~ .A CoMpo5AN7 ~ E COLUMN ~ ~ SC IO ~ dlT ~ C-) ~
(t ~ d ~ V11 ~ Vl2 ~:
'' I) UREE DE LA ~ E ~ S DE
LA COM ~ OsAN ~ E I. ~ C ~ N ~ 8R I 500 m ~ ocond ~
(tenps ~ VX b V ~
.AP <OE OF 1- '~ M1'UL8IoN I ~ E.
SENSE ~ BILISATION ~ 1 nl ~ econde ~ :: -.
3g TEME '~ RITURE ~ W: 2 uccollc1c o TEH1 '~ Bl ~ N1 ~ INI ~ IT ~ N 7'M: ~ u choice ~, 0 q! EMPS OF ERASE ~; N1 'TE: 600 m ~ condoo rURE ~ i: DU Gou} ~ R (~ uIT ~ GE ICC; ~ ~ ocond ~ s

Claims (15)

1. Process of selective formation and growth differential of a new solid phase in a selected fraction of cells in a system comprising a multiplicity of electrolysis cells, in each which one of the electrochemical reactions produced by the passage of an electric current in one direction involves the formation of said new phase, in which :

1) a cell is applied to the selected cells voltage pulse called awareness pulse higher than the electrolysis voltage threshold, 2) and later, the same voltage is applied electrolysis to all sensitized cells and not sensitized;

the process for formation and growth of the new phase in the selected cells only in the system and vice versa, the lack of training and of development of the new phase in non-cells selected in the system.

2. Method according to claim 1, characterized in what we apply the electrolysis voltage gradually according to a preferably linear increasing ramp. 3. Method according to claim 1, characterized in what we modulate the voltage of the pulse of awareness to achieve differential growth of the new phase from one cell to another. 4. Method according to claim 1, characterized in what the electrochemical reaction including training of a new phase is the electrocrystallization of a metal or an alloy by cathodic reduction of ions into solution. 5. Method according to claim 4, characterized in what we do electrocrystallization of metal or the alloy on a semiconductor electrode, in particular a tin oxide (TO) or mixed tin oxide electrode and indium (ITO) in a thin transparent layer. 6. Method according to claim 5, characterized in what the new electrocrystallized phase is bismuth or a bismuth alloy. 7. Method according to claim 5, characterized in what the new electrocrystallized phase is copper or a copper alloy. 8. Multiplexed matrix addressing method of a electrochromic or electrochemical display screen comprising a matrix of elementary cells generators of image points placed at the intersections of two orthogonal networks of electrical conductors, characterized in that it comprises the succession of stages following:

1) we proceed by passing the electric current in the direction of writing an image point, developing an electrochemical reaction involving the formation of a new solid phase, training and growth of such a solid phase being used to modulate the optical density by reflection or transmission or are combined with the formation and growth of another species used for such modulation;

2) the sequence of the phases of a cycle is carried out complete writing an image, maintaining said image displayed and erasing said image by the succession of the following phases:

a) multiplexed awareness phase of the screen - we address the lines one after the other the other ;

- while this line is addressed, we apply a voltage pulse called awareness between said line and the columns defining at the intersection with said line the image points of said image, we applies to the other columns with respect to said line a voltage below the write threshold, preferably a zero voltage or the open circuiting of said columns;

- we then do the same with the following line and so on until the last line;

we thus form on the whole screen an "image latent "in a time equal to the duration of the pulse awareness multiplied by the number of lines;

b) image writing phase we "reveal" the "latent" image by applying a write voltage between the lines all connected in electrical parallel and the columns all connected in electric parallel until the desired contrast is obtained compared to the rest of the screen;

c) image maintenance phase we maintain the written image for the duration display;

d) image erasure phase we erase the written image by applying a tension and / or by making a short circuit between the lines all connected in electrical parallel and the columns all connected in electrical parallel;

e) possible phase of restandardization of the screen We realize the restandardization of the screen in shorting the lines all connected in electrical parallel with the columns all connected in electric parallel. 9. Method according to claim 8, characterized in what the density generating electrochemical process optical is the electrocrystallization of a metal or alloy by cathodic reduction of ions in solution, in particular electrocrystallization of bismuth or an alloy of bismuth or copper or a copper alloy. 10. Method according to claim 9, characterized in that 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 including tin oxide (TO), indium oxide, mixed indium tin oxide (ITO). 11. Method according to claim 9 or 10, characterized in that the voltage of the pulse of awareness of an image point according to the gray level or of black which the image point considered must present. 12. Method according to claim 8, characterized in that we choose the redox couples involved in the electrochemical reactions of cells so as to show a difference in their redox potentials, so that the cells have an electromotive force when the image points they generate are written. 13. Method according to claim 12, characterized in compensating for any weakening of the load writing picture points written during the period of maintenance of the information displayed by application between the lines all connected in electrical parallel and the columns all connected in electrical parallel, i.e.
of voltage pulses controlled by the difference between the voltage between the two conductor networks electrical and a reference voltage, or a voltage continuous equal to a reference voltage, the voltage of reference being equal to the electromotive force of cells written before any loss. 14. Method according to claim 8, characterized in that we keep the written image for the duration display either by its intrinsic memory or by applying between the columns all connected in electrical parallel and the lines all connected in electric parallel of the controlled voltage pulses by the difference between the voltage measured between lines and columns and a reference voltage corresponding to black of the image. 15. Method according to claim 8, characterized in that we distribute the voltage of the pulse awareness in a line component and a column component Vcol with respect to the line voltage already addressed taken as a reference, such as Vligne and Vcol are each below the write threshold while that the sum Vline + Vcol is greater than this threshold and in what we apply a voltage Vcol to the columns selected and zero voltage at the columns not selected.