Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
1999-03-11
2001-01-16
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S265000, C359S270000, C524S430000, C428S457000
Reexamination Certificate
active
06175441
ABSTRACT:
The present invention relates to electrochromic devices having controllable light transmittance, their production and their use.
BACKGROUND OF THE INVENTION
Windows of vehicles have hitherto not been able to be regulated in terms of their transparency to electromagnetic radiation. Phototropic glasses have hitherto only been used for spectacles and have only a relatively small change in the transmission. Windows in buildings have hitherto been darkened using curtains, shutters, roller blinds or other movable mechanical elements. Electrochromic devices can thus be applied in many ways. In summary, examples are:
1. Vehicle Glazing (window panes or sunroofs in cars)
An electrochromic device is suitable for protection against sun or dazzling in motor vehicles. Front, side and rear windows or glass roofs cam be included. The degree of darkening can be matched zonewise and steplessly to the needs of the driver, to the state of the sun and to the current driving situation. Integration into a computerized control system is possible. A combination of the active element with a composite glazing unit is likewise possible, for example application of a film system to panes of safety glass.
SUMMARY OF THE INVENTION
The transmittance of the panes can be controlled manually or automatically, which can be used for effective protection against dazzling during night driving, automatic adjustment of the brightness level when driving in and out of tunnels and multistorey carparks and for protection against breaking-in and theft of the parked vehicle by preventing vision into the vehicle interior. Excessive heating of the interior in summer, particularly in the case of a parked vehicle, can be prevented (cf. EP-A 0 272 428).
2. Glazing of Buildings (electrochromic window)
In buildings, electrochromic assemblies are suitable for darkening side windows and skylights of buildings, dwelling rooms, workrooms or greenhouses as controllable protection against sun (visible spectral region) and heat (IR region) and for protecting the eyes (visible spectral region). For protection against break-ins, glazing of bank counters or display windows can be darkened at the press of a button. Glass doors can be made transparent automatically on approach of a person in order to avoid injury. The opportunity of producing virtually all shades of colour also makes it possible to blend the glazing into the facade of a building. The energy consumption for controlling the transparency of large areas of window is low, particularly when the memory effect of the system can be exploited and energy is only consumed in the switching phase. A combination with heat-protection glazing (K glass) is very suitable for achieving dynamic control of solar radiation through a window (“smart window”). An electrochromic system can thus contribute to regulating and limiting the energy necessary for air conditioning of a building.
The voltage supply to the system can also be provided by solar modules. A light-sensitive sensor can determine the degree of solar radiation and thus control the light transmittance.
3. Display Elements
The ability to produce attractive colours and the large-area portrayal of any contours, e.g. letters, figures, signs and symbols (able to be produced by means of suitable structuring techniques) provides advertising with an interesting medium. Decorative and informative effects are readily possible.
Apart from the possibility of arranging the system between panes of glass, there is also the alternative of using two or even only one transparent plastic film as support. This makes possible poster-like advertising media with changeable information.
Electrochromic devices can be used for small display elements such as faces of clocks or dials of measuring instruments, displays for a wide variety of applications and for large display elements such as traffic signs, advertising columns, information displays at railway stations, airports or for parking direction systems. Use as a variable delineation system (playing area boundaries, etc.) in sports halls is likewise possible.
The use of such systems is generally possible wherever information is to be made visible.
4. Optics
In optics, electrochromic systems can be used either in combination with glasses, lenses and filters of other optical instruments or as sole actively used component. Their use as lap dissolve protection for optical detection systems is likewise possible. The system is likewise suitable as controllable filter system in photographic processes.
5. Mirrors
An electrochromic device can also be used as a dimmable mirror, e.g. in an automobile as external or rear-vision mirror which can be darkened by application of an electric potential and thus prevents dazzling by the headlights of other vehicles (cf., for example, U.S. Pat. No. 3 280 702, U.S. Pat. No. 4 902 108 (Gentex), EP-A 0 435 689, U.S. Pat. No. 5 140 455). A disadvantage of systems according to the prior art (solution systems) is the colour inhomogeneity after prolonged operation (segregation), particularly in the case of large mirrors (e.g. mirrors for heavy goods vehicles). Increasing the viscosity of the solution system by addition of polymeric thickeners has been described (e.g. U.S. Pat. No. 4 902 108).
6. EMI shielding
An electrochromic device can also be used as a variable filter element for the modulation of electromagnetic radiation in certain wavelength regions.
Electrochromic devices normally comprise a pair of glass or plastic plates of which, in the case of a mirror, one is mirrored. One side of -these plates is coated with a light-transparent, electrically conductive layer, e.g. indium-tin oxide (ITO). A cell is built up from these plates by fixing them with their electroconductively coated sides facing one another; the cell between the plates contains the electrochromic system. It is tightly sealed. The two plates can be separately provided with electric contacts and controlled via the conductive layers.
The electrochromic solution systems known from the above-cited prior art contain, in a solvent, pairs of redox substances which form coloured, positively or negatively charged, chemically reactive free radicals after reduction or oxidation. Examples are the viologen systems which have been known for a longr time.
The pair of redox substances used here is in each case a reducible and an oxidizable substance. Both are colourless or have only a slight colour. Under the action of an electric potential, one substance is reduced and the other is oxidized, at least one becoming coloured. After switching off the potential, the two original redox substances are reformed, with decoloration or lightening of colour occurring.
It is known from U.S. Pat. No. 4,902,108 that suitable pairs of redox substances are those whose reducible substance has at least two chemically reversible reduction waves in the cyclic voltammogram and the oxidizable substance correspondingly has at least two chemically reversible oxidation waves. Systems of this type are suitable mainly for dimmable rear view mirrors in cars. Since these are solution systems, use in electrochromic windows is not a possibility under normal circumstances.
Also known are systems in which the actual electrochromic redox pair is dispersed in a polymer matrix (see, for example, WO-A 96/03475). The undesirable effect of segregation is suppressed here.
Combinations of inorganic electrochromic components such as WO
3
, NiO or IrO
2
are likewise known and are possibilities as components in an electrochromic window (see, for example, U.S. Pat. No. 5 657 149, Electronique International No. 276, 16 (1997); Saint-Gobain).
These inorganic electrochromic components can be applied to the conductive substrate only by vapour deposition, sputtering or the sol-gel technique. As a result, systems of this type are very expensive to produce. In the context of efforts to replace an inorganic component by an organic polymer component, electrochromic systems, for example, based on the electrically conductive polymer polyaniline (PANI) and WO
3
as complementary elect
Heuer Helmut Werner
Jonas Friedrich
Osenberg Frank
Wehrmann Rolf
Connolly Dove Lodge & Hutz LLP
Epps Georgia
Heuer
Spector David N.
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