Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-08-16
2002-03-26
Nguyen, Chanh (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C359S265000
Reexamination Certificate
active
06362806
ABSTRACT:
BACKGROUND OF THE INVENTION
The Invention concerns a method of operating an electrochromic element which consists of at least the following layers:
a first electrode layer;
first layer, in which ions can be reversibly inserted;
a transparent ion-conducting layer;
a second layer, in which ions can be reversibly inserted; and
a second electrode layer,
where the first and/or the second layer, in which ions can be reversibly inserted, is an electrochromic layer and the other of these layers acts as counter-electrode to the electrochromic layer, and where a voltage is applied to the electrode layers which induces a colour-change process, which voltage possesses values in a redox-stability range of the electrochromic layer system and the current flows through electrochromic element is measured continuously.
1. Field of the Invention
The term colour-change process denotes either forced colouring, that is to say a reduction in transmittance or reflectance of the electrochromic element, in particular in the visible region of the spectrum, or decolouring or bleaching, that is to say increasing the transmittance or reflectance. It can also however consist primarily of a change in the colour location of the transmitted or reflected radiation. Voltage values in a redox-stability range of the electrochromic layer system denotes voltages where the electrochromic layer system consisting of the electrochromic layer, the ion-conductive layer and the layer acting as counter-electrode experiences no or at all events very slight irreversible changes.
The electrochromic element incorporates at least one electrochromic layer, whose colour can be reversibly changed. This is combined as counter-electrode either with another electrochromic layer or with a transparent ion storage layer, which does not change its transparency significantly as a result of the insertion of ions. For the sake of simplicity, the two layers in which ions can be inserted are both designated below as electrochromic layers.
The layers of the electrochromic element mentioned above can also if necessary follow one another with further layers being interposed, such as for example protective layers, insulating layers, optically effective auxiliary layers, reference electrode layers, or the like. At least one of the electrode layers is a transparent layer. If the electrochromic element is to be used as a transparent window element with variable transmittance, the second electrode layer will also be transparent. If, on the other hand, the electrochromic element is to be used as a mirror with variable reflectance, one of the two electrode layers will preferably take the form of an opaque reflection layer of a suitable metal, such as aluminium or silver. It is also possible however to operate with two transparent electrode layers and to provide an additional metal reflection layer. For the sake of simplicity, only electrochromic elements with variable transmittance will be discussed, without however the Invention being restricted to this.
It is possible, by means of the voltage applied via the electrode layers to the electrochromic element, to alter its transmittance. This change generally takes place more quickly, the higher is the voltage applied. Of course, if the electrochromic element is not operated in optimum fashion, if therefore, in particular, the voltage applied is too high, it can be permanently damaged. It is then possible for the transmittance of the electrochromic element to cease being variable, or that the difference between minimum and maximum transmittance will no longer be as great as in undamaged state, under otherwise identical ambient conditions. It is also to be feared that the electrochromic element will no longer colour homogeneously, possibly irreversibly coloured or no longer colourable areas will be formed.
Above all, if a polymer electrolyte is used as ion-conductive layer, there is also a risk of the electrochromic layer delaminating, that is to say that the ion-conductive layer will become detached from the electrochromic layers in some areas.
According to the application of the electrochromic element, it will be exposed to a greater or lesser degree to wide temperature fluctuations. Thus, for example, in the case of an electrochromic element which is used in motor vehicles as window glass, roof glazing panel, or the like, it can be expected that it will operate satisfactorily at temperatures in the range of −20° C. to +80° C. Similar temperatures are to be expected in the case of applications in the outer skin of buildings, for example in the field of building curtain walls. It is known that a temperature increase will lead to reduction of the specific resistance of the system components. In particular, the resistance of the ion-conductive layer can decrease drastically with a temperature increase. If suitable measures are not taken, this can easily lead to the fact that, at high temperatures, the redox stability range of the electrochromic layer system will be exceeded and irreversible changes will occur.
2. Description of the Prior Art
From EP 0 475 847 B1, according to which the Preamble of the Patent Claim is formulated, a process for operating an electrochromic element is known, where the voltage applied to the electrochromic element is temperature-dependent. The temperature is measured directly with a thermometer, or indirectly, by a voltage pulse being generated prior to each colour-change process, by means of which with simultaneous current measurement, the resistance of the ion-conductive layer is determined, and from this the temperature of the electrochromic element is determined. According to the temperature determined, a voltage is applied to the electrochromic element for a predetermined time. When the desired transmittance is reached, the voltage is disconnected.
EP 0 718 667 A1 has as its subject a process for operating an electrochromic element which can be influenced by the user, which process can be adapted via an interface to electrochromic elements of different designs, to the ambient temperature and to the dimensions of the electrochromic element. Here, the voltage with which the electrochromic element is operated is also to be a function of the temperature. A disadvantage of the known process is that, for each individual electrochromic element, matching of the control parameters to the window dimensions must take place.
EP 0 683 419 A1 discloses a method to trigger an electrochromic element in which a current is impressed on this.
SUMMARY OF THE INVENTION
The purpose of the present Invention is to provide a process for operating an electrochromic element which will operate over a wide temperature range, which is largely independent of the area of the electrochromic element, which permits a change in transmittance over a wide range, which permits sufficiently rapid colour change, and with which a long service life of the electrochromic element can be achieved.
This problem is solved by a process in accordance with Patent claim
1
. Advantageous configurations are the subject of the Subclaims.
According to the Invention, provision is made for the current I flowing through the electrochromic element to be measured continuously, for the voltage U applied to the electrochromic element during a starting stage of the colour-change process to be increased or reduced continuously up to maximum to a final value U
max
predetermined as a function of temperature, where the temperature dependence of the final value U
max
is determined by the design of the electrochromic element, but is independent of the area to be subjected to colour change, and that the voltage U is controlled during the course of the colour-change process as a function of the current I, where the voltage U does not exceed in magnitude the magnitude of the final value U
max
. The final value U
max
can possess a different magnitude for a colouring process than for a bleaching process.
Current measurements will normally take place regularly at always the same, sufficiently short intervals of time, typically severa
Cardinal Jens
Reichmann Peter
Marshall & Melhorn LLC
Nguyen Chanh
Pilkington Deutschland AG
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