Electrochromic pane arrangement

Details Electrochromic pane arrangement Electrochromic pane arrangement

1996-01-17

1999-01-12

Epps, Georgia Y.

Optical: systems and elements

Optical modulator

Light wave temporal modulation

429192, G02F 1153

Patent

active

058597239

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of The Invention
The present invention relates generally to display devices, and in particular, to an electrochromic pane arrangement.
2. Description of the Related Art
Electrochromic pane arrangements for use as display devices are known in the art. Such electrochromic panes may typically have a first transparent electrode substrate or glass pane, a second electrode substrate or glass pane arranged parallel to and at a distance from the first glass pane, and an ion conducting layer joining the two electrode substrates. The ion layers may consist of a polymer matrix containing at least one salt including difficult to oxidize anions, and at least one dopant suitable for the provision of cations, preferably metal ions. A surface of the first electrode substrate faces toward the ion conducting layer and bears a first transparent electrode layer. Adjacent to it is an actively electrochromic layer in surface contact with the ion conducting layer. The electrochromic layer is preferably of tungsten trioxide, having a reversibly variable transparency and/or color resulting from absorption or emission of electrons via the first electrode layer and acceptance or emission of ions of the dopant from or to the ion conducting layer. A surface of the second electrode substrate faces towards the ion conducting layer and bears a second transparent electrode layer. Adjacent to it is a transparent layer in surface contact with the ion conducting layer. The transparent layer is suitable for the reversible storage of charge, preferably by ion insertion.
An electrochromic laminated pane of this type is known from DE-A 41 16 059, where the two individual panes are joined to one another by means of a polyvinylbutyral layer which represents the ion conducting layer. The polyvinylbutyral layer, which is a film of polyvinylbutyral sufficiently well-known for the manufacture of laminated safety glass panes, contains LiClO.sub.4 as dopant.
Electrochromic pane arrangements do not as a rule evidence any electrochromic properties in their freshly manufactured state, unless the electrochromic layer and/or the charge storage layer have been precharged by the insertion of positive ions. Otherwise, only after so-called preconditioning, does the pane arrangement acquire the property of variable light transmission. For the purpose of preconditioning, the pane arrangement is switched several times at low voltages and low cycle time after connection of a DC voltage. One cycle always consists of a colouration and bleaching period. During colouration and bleaching, identical or differing voltages can be applied, but with reversed polarities, where the pane incorporating the actively electrochromic layer, normally taking the form of a WO.sub.3 layer, is connected during colouration as a cathode, but on the other hand as an anode during bleaching.
A first type of preconditioning is characterized by successive increase of the switching times and of the voltages applied.
It has been found favourable at the beginning of preconditioning to choose the colouration period of longer duration than the bleaching period, as then lower transmission values can be induced in the pane arrangement in stages. This method of preconditioning leads to a high transmission range, but is very time-consuming on account of the high number of cycles, this time requirement naturally increasing the cost of manufacture of the pane arrangement.
If it is desired to avoid the considerable time involved in the type of preconditioning used in the procedure described above, it is also known in the state of the art that the individual electrode layers can be charged with lithium ions. Either the actively electrochromic layer or the above-mentioned ion storage layer is charged with for example lithium ions before assembly to form the electrochromic pane arrangement. This is done by immersing the individual pane to be preconditioned in each case in a liquid electrolyte solution and applying a DC voltage. As counter electrode, there is a metal plate

REFERENCES:
patent: 4773740 (1988-09-01), Kawakami et al.
patent: 5016991 (1991-05-01), Mason
patent: 5206756 (1993-04-01), Cheshire
patent: 5332530 (1994-07-01), Eid et al.

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