Electrode design for electrochromic devices

Details Electrode design for electrochromic devices Electrode design for electrochromic devices

1999-06-30

2003-07-22

Lester, Evelyn A (Department: 2873)

Optical: systems and elements

Optical modulator

Light wave temporal modulation

C359S265000, C359S275000

Reexamination Certificate

active

06597489

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention generally relates to devices of reversibly variable transmittance to electromagnetic radiation. More specifically, the present invention relates to an improved electrode design for electrochromic light filters and mirrors.
Devices of reversibly variable transmittance to electromagnetic radiation have been proposed as the variable transmittance element in variable transmittance light filters, variable reflectance mirrors, and display devices, which employ such light-filters or mirrors in conveying information. These variable transmittance light filters have included architectural windows, skylights, and windows and sunroofs for automobiles.
Devices of reversibly variable transmittance to electromagnetic radiation, wherein the transmittance is altered by electrochromic means, are described, for example, by Chang, “Electrochromic and Electrochemichromic Materials and Phenomena,” in
Non-emissive Electrooptic Displays,
A. Kmetz and K. von Willisen, eds. Plenum Press, New York, New York 1976, pp. 155-196 (1976) and in various parts of
Electrochromism,
P. M. S. Monk, R. J. Mortimer, D. R. Rosseinsky, VCH Publishers, Inc., New York, New York (1995). Numerous electrochromic devices are known in the art. See, e.g., U.S. Pat. No. 3,451,741 issued to Manos; U.S. Pat. No. 4,090,358 issued to Bredfeldt et al.; U.S. Pat. No. 4,139,276 issued to Clecak et al.; U.S. Pat. No. 3,453,038 issued to Kissa et al.; U.S. Pat. Nos. 3,652,149, 3,774,988 and 3,873,185 issued to Rogers; and U.S. Pat. Nos. 3,282,157, 3,282,158, 3,282,160 and 3,283,656 issued to Jones et al.
In addition to these devices, there are commercially available electrochromic devices and associated circuitry, such as those disclosed in U.S. Pat. No. 4,902,108, entitled “SINGLE-COMPARTMENT, SELF-ERASING, SOLUTION-PHASE ELECTROCHROMIC DEVICES, SOLUTIONS FOR USE THEREIN, AND USES THEREOF,” issued Feb. 20, 1990, to H. J. Byker; Canadian Patent No. 1,300,945, entitled “AUTOMATIC REARVIEW MIRROR SYSTEM FOR AUTOMOTIVE VEHICLES,” issued May 19, 1992, to J. H. Bechtel et al.; U.S. Pat. No. 5,128,799, entitled “VARIABLE REFLECTANCE MOTOR VEHICLE MIRROR,” issued Jul. 7, 1992, to H. J. Byker; U.S. Pat. No. 5,202,787, entitled “ELECTRO-OPTIC DEVICE,” issued Apr. 13, 1993, to H. J. Byker et al.; U.S. Pat. No. 5,204,778, entitled “CONTROL SYSTEM FOR AUTOMATIC REARVIEW MIRRORS,” issued Apr. 20, 1993, to J. H. Bechtel; U.S. Pat. No. 5,278,693, entitled “TINTED SOLUTION-PHASE ELECTROCHROMIC MIRRORS,” issued Jan. 11, 1994, to D. A. Theiste et al.: U.S. Pat. No. 5,280,380, entitled “UV-STABILIZED COMPOSITIONS AND METHODS,” issued Jan. 18, 1994, to H. J. Byker; U.S. Pat. No. 5,282,077, entitled “VARIABLE REFLECTANCE MIRROR,” issued Jan. 25, 1994, to H. J. Byker; U.S. Pat. No. 5,294,376, entitled “BIPYRIDINIUM SALT SOLUTIONS,” issued Mar. 15, 1994, to H. J. Byker; U.S. Pat. No. 5,336,448, entitled “ELECTROCHROMIC DEVICES WITH BIPYRIDINIUM SALT SOLUTIONS,” issued Aug. 9, 1994, to H. J. Byker; U.S. Pat. No. 5,434,407, entitled “AUTOMATIC REARVIEW MIRROR INCORPORATING LIGHT PIPE,” issued Jan. 18, 1995, to F. T. Bauer et al.; U.S. Pat. No. 5,448,397, entitled “OUTSIDE AUTOMATIC REARVIEW MIRROR FOR AUTOMOTIVE VEHICLES.” issued Sep. 5, 1995, to W. L. Tonar; and U.S. Pat. No. 5,451,822, entitled “ELECTRONIC CONTROL SYSTEM,” issued Sep. 19, 1995, to J. H. Bechtel et al. Each of these patents is commonly assigned with the present invention and the disclosures of each, including the references contained therein, are hereby incorporated herein in their entirety by reference. Such electrochromic devices may be utilized in a fully integrated inside/outside rearview mirror system for a vehicle or as separate inside or outside rearview mirror systems.
It is desirable to use reversibly variable transmittance light filters in architectural windows, skylights, and in windows and sunroofs for automobiles in order to reduce the transmittance of the filter with respect to direct or reflected sunlight during daytime, while not reducing such transmittance during nighttime. Not only do such light filters reduce bothersome glare and ambient brightness, but they also reduce fading and generated heat caused by the transmittance of sunlight through the window.
Variable transmission electrochromic devices such as windows and light filters typically include a structure similar to that shown in FIG.
1
. Specifically, they typically include first and second transparent substrates
12
and
14
, which are commonly made of glass and arranged in parallel, spaced-apart relation. The electrochromic devices also typically include first and second transparent, electrically conductive layers forming electrodes
16
and
18
provided on the interfacing surfaces of substrates
12
and
14
. A seal
20
is provided to secure the coated substrates together and to provide a chamber
22
between the coated substrates in which an electrochromic medium
24
is provided. Electrically conductive clips
26
and
28
are respectively attached to one of the coated substrates so as to be electrically coupled to one of electrode layers
16
and
18
. The electrochromic medium
24
is contained in chamber
22
. The electrochromic medium
24
is in direct contact with transparent electrode layers
16
and
18
, through which passes electromagnetic radiation whose intensity is reversibly modulated in the device by a variable voltage or potential applied to electrode layers
16
and
18
through clip contacts
26
and
28
and an electronic circuit (not shown).
The electrochromic medium
24
includes two different coloring species—a cathodic species and an anodic species, which are colorless or nearly colorless in an inactivated state. In most cases, when there is no electrical potential difference between transparent electrodes
16
and
18
, the electrochromic medium
24
in chamber
22
is colorless or nearly colorless, and incoming light (I
o
) enters through second substrate
14
, passes through transparent electrode
18
, electrochromic containing chamber
22
, transparent electrode
16
, and first substrate
12
. When a potential difference is applied between transparent electrodes
16
and
18
at the cathode, the cathodic species are reduced (i.e., accept electrons from the cathode). On the other hand, the anodic species are oxidized at the anode (i.e., donate electrons to anode
16
). As the cathodic and anodic species in electrochromic medium
24
accept and donate electrons from/to electrodes
18
and
16
, respectively, at least one of the species become colored. The anodic and cathodic species in medium
24
return to a colorless or nearly colorless state once they exchange electrons in the center portion of chamber
22
. Nevertheless, so long as a sufficient potential is applied across electrodes
16
and
18
, there is a sufficient amount of the anodic and cathodic species that are oxidized and reduced so as to color an electrochromic cell. Because the anodic and cathodic species exchange electrons in the center portion of chamber
22
and donate and accept electrons when adjacent a respective electrode
16
and
18
, the cathodic component contributing to the perceived color exists primarily adjacent cathode
18
, and the anodic component exists proximate to anode
16
. This also corresponds to the fact that the concentration of reduced cathodic species is greatest proximate cathode
18
, and the concentration of oxidized anodic species is greatest adjacent anode
16
.
Commercially available electrochromic media that is suitable for use in chamber
24
generally includes solution-phase and solid state electrochromic materials. In an all solution-phase medium, the electrochemical properties of the solvent, optional inert electrolyte, anodic materials, cathodic materials, and any other components that might be present in the solution are preferably such that no significant electrochemical or other changes occur at a potential difference which oxidizes anodic material and reduces the cathodic material other than the electrochemical oxidation

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