Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
1998-12-17
2001-04-03
Mai, Huy (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S265000
Reexamination Certificate
active
06211995
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a laminated electrochromic device, a so-called EC device and, in particular, to such a device having a protective layer positioned on one side of the electrolyte layer.
STATE OF THE ART
Electrochromic devices can be used for modulating transmittance, reflectance, scattering, and thermal emittance by means of an applied electrical field. A standard electrochromic device employs a cathodically coloring electrochromic film (such as W oxide) and an anodically coloring (such as Ni oxide) or transparent (such as Ce oxide) counter electrode brought in contact by a solid electrolyte. Examples of such devices are displays and anti-dazzling rear-view mirrors in cars.
One of the most difficult problems with practical electrochromic devices is their limited long-term durability due to chemical incompatibility between the electrolyte layer and the adjoining electrochromic film and counter electrode. Thus WO
3
—the prime candidate for the electrochromic films—is stable in a moderately acidic environment whereas it is rapidly dissolved in a basic electrolyte. On the other hand, a major contender for being the counter electrode, NiO
x
H
y
, is stable in a basic environment but unstable in an acidic one. This often causes difficulties in production of such devices since the life time is not sufficient.
At present there is no single generally accepted concept of the best way of producing EC devices.
A known possible solution to the stability problem is to invoke an additional protective layer, by means of which damage of the layers can be avoided, thereby increasing the device life time.
It is known from U.S. Pat. No. 4,120,568 to provide a “substantially insulating dielectric layer” between the electrochromic and the electrolyte layer. The materials employed for this purpose are, for instance, SnO, SiO, SiO:Au, TiO and CrN.
It is also known to use non-aggressive electrolytes to obtain sufficient life times without using any protective layers.
There are, however, many chemically aggressive electrolytes of interest for use in EC devices due to their good electrical and optical properties, which electrolytes cannot be used in conventional EC devices.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a solution to the chemical incompatibility problem in EC devices by means of a protective layer of well-suited material positioned on one side of the electrolyte layer, thus increasing the life time of devices.
According to the invention, an EC device comprises three layers of electrochromic materials, of which one acts as a protective layer. Device thereby produced use the same material for both the electrochromic or counter electrode layer and the protective layer, wherein the protective layer remains transparent and does not affect the coloration and bleaching of the device. The optical inactivity of the protective layer relies on the fundamental energetics of the multi-layer structure and is not a trivial consequence of having a thin-and hence only weakly coloring-layer.
The device may be operated in a light transmitting as well as a light reflecting mode.
According to a preferred embodiment of a device according to the invention, WO
3
and NiO
x
H
y
are employed as the protective layers in devices with acidic and basic electrolyte, respectively.
REFERENCES:
patent: 5673150 (1997-09-01), Ono et al.
patent: 5793518 (1998-08-01), Lefrou et al.
patent: 5838483 (1998-11-01), Teowee et al.
Azens Andris
Granqvist Claes-Goran
Kullman Lisen
Vaivars Guntars
Veszelei Monica
Forkarpatent 1 Uppsala AB
Mai Huy
Young & Thompson
LandOfFree
Electrochromic device comprising tandem layers of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrochromic device comprising tandem layers of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrochromic device comprising tandem layers of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2530454