Electrochromic light valve and method of manufacturing it as wel

Details Electrochromic light valve and method of manufacturing it as wel Electrochromic light valve and method of manufacturing it as wel

1993-11-12

1997-05-20

Epps, Georgia Y.

Optical: systems and elements

Optical modulator

Light wave temporal modulation

G02F 101

Patent

active

056317654

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to an electrochromic light valve with an active electrochromic layer, i.e. one whose colour can change, and a passive electrochromic layer, i.e. one whose colour essentially remains unchanged, between which an electrolyte is arranged and each of which is connected to an associated electrode, at least one of which is transparent, the coloration of the active electrochromic layer being reversibly changeable by acceptance or donation of electrons via its associated electrode and of ions of a particular element or several particular elements via the electrolyte, the passive electrochromic layer simultaneously donating ions of the species concerned of the element or the elements to the electrolyte or accepting them from the electrolyte.
The invention also relates to a method of manufacturing an electrochromic light valve of this kind in which a passive electrochromic layer is produced which contains at least one of the elements which provide the ions of the species concerned.
The invention also relates to particularly advantageous uses of this electrochromic light valve.
Electrochromic light valves are known, for example, from FR 2 633 609 A1, GB 2 081 922 A1, WO 91/02282, EP 0 323 006 A2 and DE 40 10 285 A1.
Electrochromic light valves of the kind described above can operate according to one of the following two alternative mechanisms: layer becoming coloured by accepting electrons from the electrode on one of its layer sides and positive ions from the electrolyte adjacent to its other layer side, the resulting depletion of positive ions in the electrolyte being compensated by the passive electrochromic layer supplying positive ions of the same element or another element to the electrolyte and simultaneously donating electrons to the outside via its electrode. This mechanism operates for example in an electrochromic light valve whose active electrochromic layer essentially consists of tungsten trioxide (WO.sub.3) and in which the ions are lithium ions (Li.sup.+) for example. This mechanism can also function with negative ions instead of positive ions, in which case when becoming coloured the active electrochromic layer donates negative ions to the electrolyte and the passive electrochromic layer accepts negative ions of the same element from the electrolyte. layer becoming coloured by donating electrons to the outside via its electrode and simultaneously accepting negative ions from the electrolyte via its interface with the electrolyte or donating positive ions to the electrolyte, the resulting ion depletion or ion excess in the electrolyte being compensated by the passive electrochromic layer donating ions of the species concerned of the same element or another element to the electrolyte and/or accepting them from the electrolyte and receiving electrons from outside in each case via its electrode. As an example of positive ions being donated when the active electrochromic layer is being coloured the literature quotes a system in which the active electrochromic layer essentially comprises iridium oxide (IrO.sub.x) whilst acceptance of negative ions by the active electrochromic layer when being coloured takes place for example in a system in which this layer essentially comprises nickel oxide (NiO.sub.x).
An electrochromic light valve of the kind described above, in which the active electrochromic layer can be reversibly coloured by accepting electrons from its electrode and positive ions of a particular element from the electrolyte, the passive electrochromic layer donating positive ions of the element to the electrolyte and/or accepting them from the electrolyte, is for example known from FR 2 633 609 A1 and the paper "Dip-coated CeO.sub.2 -TiO.sub.2 films as transparent counter-electrode for transmissive electrochromic devices" by P. Baudry, A. C. M. Rodrigues and M. A. Aegerter, which is published in Proc. Vth Int. Workshop on Glasses and Ceramics from Gels, Rio de Janeiro, 6-10 Aug. 1989, and also from GB 2 081 922 A in a non-transparent form

REFERENCES:
patent: 5007718 (1991-04-01), Minoura et al.
"Transmissive Electrochromic Device", Junichi Nagai et al., Solar Energy erials, Nov. 1986, Nos. 3-5, , pp. 175-183, Amsterdam, The Netherlands.
"Display Devices", Table of Contents, Springer-Verlag, N.Y. 1980.

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