Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1994-10-07
1996-12-17
Ben, Loha
Optical: systems and elements
Optical modulator
Light wave temporal modulation
359275, 359315, 359321, G02F 115
Patent
active
055859585
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention concerns electrochromic light modulation devices, in particular devices for variable light reflection, variable light transmission, and the display of signals and images, for example, the display of alphanumeric or graphic information. By way of example, these devices include display panels and screens of the most varied dimensions and shapes, windows, showcases, screens, windscreens, spectacles with variable transparency, and mirrors with variable reflection.
BACKGROUND OF RELATED ART
Numerous electrochromic processes have been proposed and described for modulating light in transmission or reflection in order to display signals and images. These processes provide displays, screens, mirrors or other objects which, totally or partially, reflect or transmit light according to instructions transmitted to them by electrical means.
These electrochromic processes function in accordance with the laws of reversible electrolysis and use the reversible change in color and/or of optical density obtained by electrochemical oxydo-reduction of a so-called "electrochromic" material, the oxidized form and the reduced form of which are of different colors and/or optical densities.
Basically, an elementary light modulating cell, which functions according to an electrochromic process, comprises two electrodes separated by an electrolytic medium consisting of one or several layers. One of the electrodes at least (in the case of a reflection function) should be transparent. Various devices well known to those of ordinary skill in the art protect the electrodes, transmit the current, protect the layer(s) of the electrolyte, and provide the geometric shape of the cell. French patent FR-B-2 618 567 describes such a device for the light modulating.
Electrochromic light modulation processes afford a group of characteristics which may be advantageous for certain applications and which have often been cited. In particular, the following advantages exist: of the electrolytic medium and which may therefore be reduced even further for certain uses. processes, to obtain an excellent contrast, even in side vision with a high angle. Contrary to the situation with some processes which operate by transmission of polarized light, and those which have poor visibility in daylight, this process is very suitable for electrochromic display units-operating by reflection, even when they are placed outside in strong sunlight.
The practical achievement of these advantages is subject, however, to the solution of certain operating difficulties which the different processes proposed are intended to reduce.
Thus, for example, the need to avoid deterioration, indeed the disappearance of the electrolytic medium, resulting in the degradation and the inadequate lifetime of the cell, is at the basis of a large number of proposals regarding the choice of the electrolytic layer(s), and the practical creation of rigorously sealed cells. Other problems concern the practical difficulty of installing the components of the electrolytic medium. For example, it is very difficult, if not impossible, to obtain, with an electrolytic liquid, electrochromic cells of very small dimensions. The following procedure is used at present, in particular in the case of small pixel screens or displays obtained from transparent "columns" and "lines" on a non-transparent base:
The transparent electrode is created from a conductive transparent layer which is itself deposited onto a transparent substrate, such as glass or a transparent plastic material. This transparent conductive layer is made up of one or several metals or oxides, such as, for example, gold, silver, tin oxide (TO), indium tin oxide (ITO), zinc oxide and cadmium stannate etc, as mentioned in the literature. In order to remain transparent, these layers must be very thin (some hundredths to some thousandths of an Angstrom). Various very well known processes are therefore used very economically to deposit these materials, such as spraying powders or liquids which decompose on to th
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Ben Loha
Compagnie Generale D'Innovation Et De Developpement Cogidev
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