Method and arrangement for supplying a system of electro-optic layers with an operating voltage.

p0001The invention relates to a defined in the preamble of claim 1. A method for applying an electrical drive voltage to an electro-optic layer system for changing an optical property of this system. Furthermore, the invention relates to a defined in the preamble of claim 6 arrangement with an electro-optic layer system.

p0002Such methods and arrangements are known in connection with electro-optical layers which are arranged in particular between coated glass surfaces or other transparent insulators and are operated in such a way that an electrical current flow can be generated in the electro-optical layers through both sides of the electro-optical layers deposited conductive layers, wherein an optical property of at least one of these layers change reversibly. Under the influence of an electric current changes, for example in an electrochromic cell or slice of spectral transmittance or reflection area, ie the coloring at least one of the electro-optical layers.

p0003To generate the electric current flow an external potential difference between the terminals of the conductive layers is manufactured. The terminals are usually arranged on opposite sides of a plane perpendicular to the electro-optical layers reference plane, preferably such that upon application of the external potential difference across train located in the cross section of the conducting layers and the electro-optical layers current paths of equal length to the reference plane, whereby a spatially gleichäßige optical effect - for example, coloring or bleaching an electrochromic cell - is achievable.

p0004An inner potential difference between two opposite, separated by the electro-optical layers points of the first and the second conductive layer may not exceed a given threshold, for example 1.5 volts, otherwise the electro-optic layer system would irreversibly damaged. To ensure that this limit for the inner potential difference, in the prior art, the external potential difference is limited (at the terminals of the conductive layers) on this limit, resulting in no disadvantage in static operation of the electro-optical layers.

p0005In dynamic operation, however, there is the problem that a desired optical state change - for example, coloring of an electrochromic cell upon application of a potential difference or lightening the electrochromic cell in eliminating or reversing the potential difference - for some applications is not fast enough proceeds.

p0006The invention solves the task of improving generic methods and arrangements so that a more rapid change in the optical state of the electro-optic layer system is made possible.

p0007As regards the method this object is achieved in that the external potential difference is chosen initially greater than the limit for the inner potential difference when applying the electrical charge and will only be returned to or below the threshold.

p0008By the initial elevation of the external potential difference over the limit, the advantage is achieved that a desired optical state change of the electro-optical layers - without damage to these - is reached more quickly, irrespective of the size or area of ​​the electro-optical layers.

p0009This beneficial effect is due to the following facts: If applying a DC voltage as an external potential difference between the Leitschichtanschlüssen, so a charge or discharge current flows into the layer system: the serving Because the electrical resistance as injections, for aesthetic reasons but extremely thin conductive layers formed on these along a voltage drop that can decrease the inner acting on the electro-optical layers potential difference to a value below the external potential difference.

p0010When the external potential difference just the limit value, is to the electro-optical layers, although after the decay of (Ent) charging current of the full limit value, during (un) loading operation, however, only the remaining after subtraction of the residual voltage drop value is available. The maximum possible speed for the (un) loading and thus the optical change of state is therefore not achieved in this case, especially not in larger cells with correspondingly long flow paths and large voltage drops.

p0011you now increase the duration of the (un) charging current, the outer potential difference, the voltage drop associated with the current flow can be compensated, so that the inner potential difference can remain close to the limit. The (un) loading process is accelerated without danger to the electro-optical layers. Its duration depends in extreme cases, from only the electrical resistance of the electro-optic layer system.

p0012For task-solving performing first of two basic inventive process variants, an arrangement is also proposed, which has a third terminal for detecting an electric Meßpotentials the second conductive layer, wherein this connection on the same side of the reference plane as the first terminal.

p0013When the inner potential difference is detected by means of the third terminal, the external potential difference can be advantageously controlled directly in dependence on the detected value so that the internal potential difference does not exceed the limit value, even though the external potential difference can take at the start of the application of a multiple of the limit value ,

p0014For safety's sake it can be provided that at least one further internal potential difference is detected and the external potential difference as a function of the detected values ​​is controlled so that none of the internal potential differences exceeds the limit value.

p0015On the other hand - in a second basic variant of the method according to the invention - the external potential difference as a function of time and - is optionally not carried out in a narrow temperature range - also controlled by the temperature of the electro-optical layers in such a way that it follows a predetermined curve over the time , a third terminal advantageously not even necessary, that is, in this case, a conventionally-equipped electro-optic layer system can be operated by the inventive method.

p0016Due to the above-mentioned physical facts, it is possible in the sense of a rapid change of state of the electro-optical layers advantageous when the external potential difference is regulated or controlled so that the internal potential difference or the internal potential differences run as close to the limit value. An initial external voltage overshoot accelerates However, in any case, the (un) loading of the electro-optic layer, even if the permissible limit for the (inner) potential difference is not utilized in full. For some applications, a change speed may be sufficient, which is between that of a static operation (external potential difference = the limit value) and the maximum speed (internal potential difference = the limit value). Where such an intermediate solution is sufficient, you can save on costs for the generation of a maximum inflated outer potential difference.

p0017Referring to the drawing illustrated embodiments, the invention is explained in more detail below. It shows<dl id="dl0001"><dt>Fig. 1</dt><dd>a schematic section through an inventive cell with an electro-optic layer system;</dd><dt>FIG. 2</dt><dd>a diagram of the spatial potential gradient to the conductive layers of an electro-optic layer system in the presence of an initial charging current;</dd><dt>Fig. 3</dt><dd>a diagram of the spatial potential gradient to the conductive layers of an electro-optic layer system at abgeklungenem charging current;</dd><dt>Fig. 4</dt><dd>a diagram of the temporal course of the external potential difference between the supply terminals of the conductive layers according to the invention in operation;</dd><dt>Fig. 5</dt><dd>a first voltage supply means for generating an external potential difference according to the invention; and</dd><dt>Fig. 6</dt><dd>a second voltage supply means for generating an external potential difference according to the invention;</dd></dl>

p0018The schematic section according to Figure 1 shows an example of a cell or disc with an electrochromic layer system S (WO₃ - electrolyte - back electrode) between two glass plates G1, G2. In a first (in the Figure upper) surface of the electro-optic layer system S a first electrically conductive, linear or sheet-like conductive layer is applied L1 (eg indium tin oxide), and on a second (in the figure lower) surface of the electro-optical layer system S is applied a second electrically conductive, linear or sheet-like conductive layer L2. To the first conductive layer L1, an electric potential can be via a first terminal A are placed, and to the second conductive layer L2 may have a second terminal B, an electric potential can be set, wherein the first (A) and the second (B) terminal on opposite sides of a normal to the electro-optic layer system S, imaginary reference plane e are arranged, preferably on opposite edges of the assembly, and preferably such that in phantom by applying an external potential difference δPa between the first (a) and the second (B) terminal drawn, by the reference plane e passing current paths of the same length can be formed.

p0019The arrangement according to Figure 1 further comprises a third terminal for detecting an electric C Meßpotentials the second conductive layer L2, the third port C on the same side of the reference plane as the first terminal E is A. Finally, the arrangement according to Figure 1 or a fourth port D for detecting an electric Meßpotentials the first conductive layer L1, the fourth terminal D on the same side of the reference plane e is as the second terminal B. In Figure 1 is a coordinate axis x located below the sectional image of the arrangement, on the will now be made in describing the spatial potential gradients on the conductive layers L1, L2 reference.

p0020If an external potential difference δPa applied between the first terminal A of the first conductive layer L1 and the second terminal B of the second conductive layer L2, it comes in the manner explained above to a charging or discharging current, which on its way through the resistive thin conductive layers L1, L2 a value dependent on the length of the path voltage drop causes. An initial (ent) charging current flowing to the beginning of application of the external potential difference δPa, therefore, leads to the in Fig.2 as an inclined straight line P1 applied to the x-axis spatial potential variation on the conductive layer L1, in which case the potential at the terminal B is defined as zero. At the same time gives the initial (ent) charge current to as an inclined straight line P2 coated on the x-axis spatial potential variation on the conductive layer L2. The difference between the potentials P1 and P2 at a coordinate x is the existing potential difference there inner δPi that actually exists at this point between two opposing points of the conductive layers L1, L2, and acts on the electro-optic layer system S.

p0021As shown in Figure 2 can be seen, the inner potential difference is δPi during a charging current flow due to the voltage drops in the conductive layers L1, L2 substantially lower than the external potential difference δPa. So come when the external potential difference δPa the inner potential difference δPi is chosen only as large as the threshold Umax, an unnecessary and undesirable low voltage value to the electro-optic layer system S. However, you now select the external potential difference δPa for the duration of the charging current flow considerably higher as the limit Umax, so also the reaching of the electro-optic layer system S subvoltage δPi the permissible limits, ie cause the threshold Umax, nor exploit (potentiostatic operation) and therefore the fastest possible (Ent) charge of the electro-optic layer system S.

p0022After the (Ent) charging current has subsided, there is in the conductive layers L1, L2 not covered significant voltage drops more, so that - as shown in Figure 3 - the potentials P1, P2 of the conductive layers L1, L2 are constant over the x-axis. The inner potential difference δPi then does not differ substantially from the outer potential difference δPa. In this static state, the outer potential difference δPa must therefore be not greater than the limit Umax.

p00234 shows schematically simplified 2 exemplary temporal profiles of the external potential difference δPa that cause the one hand a fast (Ent) charge of the electro-optic layer system S on the other hand does not result in exceeding the limit value Umax of the inner potential difference δPi. As can be seen, the external potential difference δPa is at a certain temperature θ₁ for the (Ent) charging time corresponding time t1 with respect to the limit value Umax excessive and is then fed back to this value. At a lower temperature θ₂ the duration of the (un) load on t2 extended.

p00245 shows this is a circuit diagram of a first power supply means for generating an external potential difference δPa with the required properties, namely always to be as large as possible, but never so great that the internal potential difference δPi would exceed the limit value Umax.

p0025This Spannungsversorgungseinrirchtung works with a closed control loop. A control unit R at an output a varying (DC) voltage to the terminal A of the conductive layer L1 ready. When the terminal B of the conductive layer L2 is set at zero potential, the voltage at terminal A the same time, the outer potential difference δPa. The actual value of an internal potential difference δPi can now, for example, measured as the potential at the fourth terminal D of the arrangement of Figure 1 and a first summing Q1 supplied, where a comparison with the limit value Umax takes place. A possible deviation is usually unit R fed and minimized by this, so that the internal potential difference δPi is maintained at the limit value Umax. Furthermore, a further internal potential difference δPi be calculated by dividing the measured potential at the terminal C by means of a second summing element Q2 is subtracted from the potential applied to the terminal A. This inner potential difference δPi turn can be controlled by comparison with the threshold Umax at or below the limit value Umax, by the control unit R its output voltage, ie, the outer potential difference δPa, adapts in the sense of minimizing a deviation. If two internal potential differences δPi be detected, neither the limit Umax exceed. In inhomogeneous potential distribution across the width x of the electro-optic layer system S thus the largest measured inner potential difference δPi is the control criterion for the control unit R. The scheme brings with her feedback of actual values ​​a high degree of safety against overvoltage inside the assembly.

p0026If a value suitable for a fast (Ent) charge the electro-optic layer system S temporal and optionally temperature-dependent profile of the external potential difference δPa are known - for example those shown in Figure 4 - can be even without feedback of actual values ​​of the external potential difference δPa in function of time and optionally controlling the temperature so that this potential difference δPa follows a predetermined curve over time.

p0027Figure 6 symbolizes such a voltage supplying means to the timed generation of the external potential difference δPa.

p0028Since the ideal time profile of the external potential difference δPa even of one parameter, namely the temperature of the electro-optic layer system S, depends on the specification of a parameterized family of curves can be provided and the appropriate voltage-time curve as a function of the sensed parameter is automatically selected and set will.

p0029In the case of time control eliminates the need for a feedback of actual values ​​of the internal potential difference δPi, and thus also requires no third (C) or the fourth (D) terminal of the conductive layers L1, L2 to be provided. It can therefore also be conventionally equipped layer arrangements according to the method of initially inflated outer potential difference δPa operated and transferred more quickly into the respective complementary optical condition.