CA2340083C - Reversible electrochemical mirror (rem) with improved electrolytic solution - Google Patents
Reversible electrochemical mirror (rem) with improved electrolytic solution Download PDFInfo
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- CA2340083C CA2340083C CA002340083A CA2340083A CA2340083C CA 2340083 C CA2340083 C CA 2340083C CA 002340083 A CA002340083 A CA 002340083A CA 2340083 A CA2340083 A CA 2340083A CA 2340083 C CA2340083 C CA 2340083C
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/15—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on an electrochromic effect
- G02F1/1506—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on an electrochromic effect caused by electrodeposition, e.g. electrolytic deposition of an inorganic material on or close to an electrode
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/15—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on an electrochromic effect
- G02F1/153—Constructional details
- G02F1/155—Electrodes
Abstract
A reversible electrochemical mirror (REM) includes a first electrode (106) a nd a second electrode (110), one of which is substantially transparent. An electrolytic solution (112), disposed between the first and second electrode s, contains ions (116) of a metal which can electrodeposit on the electrodes depending on the applied potential. The electrolytic solution also contains halide and/or pseudohalide anions having a total molar concentration ratio o f at least 6:1 compared to that of the electrodepositable metal. It is usually necessary to apply a surface modification layer (108) to the firs electrode to ensure uniform nucleation so that a mirror electrodeposit having high reflectivity is obtained.
Description
_ WO O110b312 PCT/US00116858 REVERSIBLE ELECTROCHEMICAL MIRROR (REM) WITH IMPROVED
ELECTROLYTIC SOLUTION
BACKGROUND OF THE INVENTION
Field of the Invention This invention is concerned with devices, such as mirrors and windows, having controllable reflectivity.
Description of the Related Art Sunlight transmitted through windows in buildings and transportation vehicles can generate heat (via the greenhouse effect) that create; an uncomfortable environment and increases air conditioning requirements and costs. Current approaches to providing "smart windows'°
with adjustable transmission for use; in various sunlight conditions involve the use of light absorbing materials.
These approaches are only partially effective, since the window itself is heated and because these devices, such as electrochromic devices, are relatively expensive and exhibit limited durability and cycle life. Certain liquid crystal-based window systems switch between transmissive and opaque/scattering states, but these systems require substantial voltages to maintain the transparent state.
There is an important need for an inexpensive, durable low voltage smart window with variable reflectivity.
Reflecting the light, rather than absorbing it, is the most efficient means for avoiding inside heating.
In prior art attempts t:o exploit reversible electrodeposition of a metal for light modulation, the deposits obtained on transparent substrates presented a rough and black, gray, or somet~.mes colored appearance .typical of finely-divided metals) and exhibited poor reflectivity and high light absorbance, especially when thick. Sucn deposits have been investigated for display applications involving reflectance from the background, ~r~th white pigments often being added to improve contrast.
s~Varszawski (U. S. Patent No. 5,05&,899), which is cancerned with displays, teaches than reversible metal electrodeposition is most appropriate for display applications, since significant disadvantages for transmission devices were given (e.g., the possibility of ~5 metal deposition at the counter eletarade). Such teachings imply that the application of reversible metal deposition to smart windows must involve light absorption by the finely divided electrodeposited metal, which would result in heating of the device itself and thus the space inside.
The low reflectance of this type of deposit would not be appropriate for adjustable mirror a~?plications. The prior art literature also teaches that, for transmission-type devices, reversible metal electrodeposition requires the use :~f an auxiliary counter electrode reaction; otherwise, metal would plate on the counter electrode as the deposit was de-plated from the working ~elec~trode.
Electrolytes described in the prior art literature contain auxiliary redox species (e.c~., bromide, iodide, or chloride) that are oxidized (e.g., to bromine, iodine, or chlorine) at the counter electrode during metal depasition under the high drive voltages used. This introduces chemistry-related instabilities during long term operation and leads to deposit self erasure on open circuit via chemical dissolution of the metal deposit, e.g., 2Ag° + Br=
---> 2AgBr. In most cases, this auxiliary redox process WO O1/Ob312 PCTlUS00/16858 .. 3 hinders metal deposition .at the ~~ounter electrode during erasure, introducing a threshold voltage that is desirable for display applications. This au:~iliary redox process may represent a significant' side reaction even. when metal .. alat~ng/deplating occurs at the counter electrode and a threshold voltage is not observed. See, e.g., Warszawski, columns 3-4 !when copper or nic~;el were present in the counter electrode paste? and Duchyne et al., Electrolytic Display, IEEE Transactions on Electron Devices, Volume ED-1C 26, Number 8, Pages 1243 -1245 (August 1979); French Patent No. 2,504,290 (October 22, 1982). High switching voltages of at least 1 V were used for a1.1 the electrodeposition devices which have been found in the patent and literature prior art.
15 A paper by Ziegler et al. (Electrochem. Soc. Proc.
Voi . 93-26 ( 1993 ) , p . 353 ) describes an investigation for display applications of the reversible electrodeposition of bismuth in aqueous solutions containing a large molar concentration ratio of halide anions to the trivalent ?C bismuth ion. Halide anion oxidation served as the counter electrode reaction with the 1.5 volt write voltage used.
The deposits obtained were dark in color and were shown to decrease the reflectance of the I'TO surface. Subsequent reports by these authors (Electrochem. Soc. Proc. Vol. 94-25 31 (1994), p: 23; Solar Energy Mater. Solar Cells ~9 19951, p. 317) indicated that~addition of copper ions to the electrolyte was necessary to .attain complete deposit erasure. Thus, Ziegler et al. do not teach that a significant improvement in the deposit quality or 30 erasability can be derived from use of a high molar concentration ratio of halide anion to electrodepositable metal ion in the electrolyte. These authors utilized a counter electrode reaction other than metal electrodeposition/dissolution and never obtained a mirror 3~ deposit.
WO 01106312 PCTIITSOOlI6858 Warszawski teaches that the use of a grid counter electrode would give a less uniform deposit since deposition on the transparent working electrode is highly localized in the vicinity of the counter electrode arid _ones !a consequence of the very thin film of gel electrolyte usedi. Warszawski als~a teaches the use of an aqueous gel electrolyte to minimize sensitivity to atmospheric contaminants and to avoid the necessity of navina a leak tight seal. Such electrolytes, however, have 1C much more limited temperature and voltage operating ranges compared with organic-based electrolytes with high boiling sclvenis.
One effort to improve the deposit quality of the electrolytic solution used in a reversible ~5 electrodeposition process, described in U.S. Patent No.
5,764,402 to Udaka et al.), requires the addition of organic additives to the solution. Unfortunately, such additives are typically destroyed during the electroplating process, greatly limiting cycle life. Furthermore, this 20 approach fails to produce highly-reflective mirror-like deposits, which, due to their superior heat-rejecting c:~aracter~stics, are desirable for many applications.
TJ.S. Patent 5,880,872 to Udaka teaches that the "working" electrode of a reversible electrodeposition 25 structure is degraded, and its working life thereby shortened, by the high voltage required to dissolve the metal film deposited upon it. U<iaka states that this consequence can be avoided by adding an alkali metal halide to the device's electrolytic solution, preferably in an 30 amount which provides an alkali mE~tal halide to silver halide ratio of between 0.5 to 5. lHowever, the described electrolytic formulation fails to provide the inherent stabil:.ty, high quality deposits, good erasure and long cycle life needed for practical applications. Mirror .. deposits taere never obtained.
ELECTROLYTIC SOLUTION
BACKGROUND OF THE INVENTION
Field of the Invention This invention is concerned with devices, such as mirrors and windows, having controllable reflectivity.
Description of the Related Art Sunlight transmitted through windows in buildings and transportation vehicles can generate heat (via the greenhouse effect) that create; an uncomfortable environment and increases air conditioning requirements and costs. Current approaches to providing "smart windows'°
with adjustable transmission for use; in various sunlight conditions involve the use of light absorbing materials.
These approaches are only partially effective, since the window itself is heated and because these devices, such as electrochromic devices, are relatively expensive and exhibit limited durability and cycle life. Certain liquid crystal-based window systems switch between transmissive and opaque/scattering states, but these systems require substantial voltages to maintain the transparent state.
There is an important need for an inexpensive, durable low voltage smart window with variable reflectivity.
Reflecting the light, rather than absorbing it, is the most efficient means for avoiding inside heating.
In prior art attempts t:o exploit reversible electrodeposition of a metal for light modulation, the deposits obtained on transparent substrates presented a rough and black, gray, or somet~.mes colored appearance .typical of finely-divided metals) and exhibited poor reflectivity and high light absorbance, especially when thick. Sucn deposits have been investigated for display applications involving reflectance from the background, ~r~th white pigments often being added to improve contrast.
s~Varszawski (U. S. Patent No. 5,05&,899), which is cancerned with displays, teaches than reversible metal electrodeposition is most appropriate for display applications, since significant disadvantages for transmission devices were given (e.g., the possibility of ~5 metal deposition at the counter eletarade). Such teachings imply that the application of reversible metal deposition to smart windows must involve light absorption by the finely divided electrodeposited metal, which would result in heating of the device itself and thus the space inside.
The low reflectance of this type of deposit would not be appropriate for adjustable mirror a~?plications. The prior art literature also teaches that, for transmission-type devices, reversible metal electrodeposition requires the use :~f an auxiliary counter electrode reaction; otherwise, metal would plate on the counter electrode as the deposit was de-plated from the working ~elec~trode.
Electrolytes described in the prior art literature contain auxiliary redox species (e.c~., bromide, iodide, or chloride) that are oxidized (e.g., to bromine, iodine, or chlorine) at the counter electrode during metal depasition under the high drive voltages used. This introduces chemistry-related instabilities during long term operation and leads to deposit self erasure on open circuit via chemical dissolution of the metal deposit, e.g., 2Ag° + Br=
---> 2AgBr. In most cases, this auxiliary redox process WO O1/Ob312 PCTlUS00/16858 .. 3 hinders metal deposition .at the ~~ounter electrode during erasure, introducing a threshold voltage that is desirable for display applications. This au:~iliary redox process may represent a significant' side reaction even. when metal .. alat~ng/deplating occurs at the counter electrode and a threshold voltage is not observed. See, e.g., Warszawski, columns 3-4 !when copper or nic~;el were present in the counter electrode paste? and Duchyne et al., Electrolytic Display, IEEE Transactions on Electron Devices, Volume ED-1C 26, Number 8, Pages 1243 -1245 (August 1979); French Patent No. 2,504,290 (October 22, 1982). High switching voltages of at least 1 V were used for a1.1 the electrodeposition devices which have been found in the patent and literature prior art.
15 A paper by Ziegler et al. (Electrochem. Soc. Proc.
Voi . 93-26 ( 1993 ) , p . 353 ) describes an investigation for display applications of the reversible electrodeposition of bismuth in aqueous solutions containing a large molar concentration ratio of halide anions to the trivalent ?C bismuth ion. Halide anion oxidation served as the counter electrode reaction with the 1.5 volt write voltage used.
The deposits obtained were dark in color and were shown to decrease the reflectance of the I'TO surface. Subsequent reports by these authors (Electrochem. Soc. Proc. Vol. 94-25 31 (1994), p: 23; Solar Energy Mater. Solar Cells ~9 19951, p. 317) indicated that~addition of copper ions to the electrolyte was necessary to .attain complete deposit erasure. Thus, Ziegler et al. do not teach that a significant improvement in the deposit quality or 30 erasability can be derived from use of a high molar concentration ratio of halide anion to electrodepositable metal ion in the electrolyte. These authors utilized a counter electrode reaction other than metal electrodeposition/dissolution and never obtained a mirror 3~ deposit.
WO 01106312 PCTIITSOOlI6858 Warszawski teaches that the use of a grid counter electrode would give a less uniform deposit since deposition on the transparent working electrode is highly localized in the vicinity of the counter electrode arid _ones !a consequence of the very thin film of gel electrolyte usedi. Warszawski als~a teaches the use of an aqueous gel electrolyte to minimize sensitivity to atmospheric contaminants and to avoid the necessity of navina a leak tight seal. Such electrolytes, however, have 1C much more limited temperature and voltage operating ranges compared with organic-based electrolytes with high boiling sclvenis.
One effort to improve the deposit quality of the electrolytic solution used in a reversible ~5 electrodeposition process, described in U.S. Patent No.
5,764,402 to Udaka et al.), requires the addition of organic additives to the solution. Unfortunately, such additives are typically destroyed during the electroplating process, greatly limiting cycle life. Furthermore, this 20 approach fails to produce highly-reflective mirror-like deposits, which, due to their superior heat-rejecting c:~aracter~stics, are desirable for many applications.
TJ.S. Patent 5,880,872 to Udaka teaches that the "working" electrode of a reversible electrodeposition 25 structure is degraded, and its working life thereby shortened, by the high voltage required to dissolve the metal film deposited upon it. U<iaka states that this consequence can be avoided by adding an alkali metal halide to the device's electrolytic solution, preferably in an 30 amount which provides an alkali mE~tal halide to silver halide ratio of between 0.5 to 5. lHowever, the described electrolytic formulation fails to provide the inherent stabil:.ty, high quality deposits, good erasure and long cycle life needed for practical applications. Mirror .. deposits taere never obtained.
prior art literature teaches that the memory effect is ~e:nporary. This is a consequence of the occurrence of a ~o~zn~er electrode reaction other than meta~w pla~~.ng/deplating. The energetic oxidation products 5 generated at the counter electrode can cause dissolution of the metal deposit on the working electrode either c:~em~catly or, open circuit (slow) or electrochemically aur~na short circuit ifasti.
Nishikitani et al. (European Patent No. 0,618,477) teaches that the counter electrode in electrochromic devices for smart window applications can be a metal grid which is substantially. transparernt. Since no metal electrodeposition occurs in el.ectrochromic devices, however, the grid in this case is used to provide a I5 transparent electrode, not to maintain transparency by localizing metal deposition. In addition, to provide adequate electrical capacity for electrochromic dev.~ces, Nishikitani's grid would need a very high surface area (at least 10 m~/g and preferably 50 to 5,000 m2/g) and a line width of 50 to 5,000 um; alternatively, a plurality of dots on a conducting substrate can be used, but the dots must contain fine particles having electrical capacitance of not less than 1 farad/g.
SUMMARY OF THE INVENTION
The reversible electrochemical mirror (REM) device of this invention permits efficient and precise control over the reflection of visible light and other electromagnetic radiation. The mirror device includes a first electrode, on which a mirror deposit is reversibly plated and dissolved, and a second electrode at which occurs the reverse of the metal piating/dissolution process occurring at the first electrode. At least one of the electrodes (and its substrate) is substantially transparent to at least a portion of the spectrum of electromaanetyc - WO 01!06312 PCT/US00/16858 radiation. Typically, the, transparent electrode is indium tin oxide (ITO) or fluorine doped t:in oxide (FTO) deposited or. a Transparent glass (or plastic? pane which serves as tine substrate. An electrolytic: solution .is disposed _ betweer. the first and second electrodes such that ions of a metal which can electrodeposit on these electrodes are soluble in the electrolytic solut:ion. The electrolytic solution described herein provides the inherent stability, high deposit quality, complete deposit erasure and long cycle life needed for practical applications.
When a negative electrical potential is applied to the first electrode relative to the second electrode, the applied potential causes deposited metal to be dissolved from the second electrode into the electrolytic solution and to be electrodeposited from the solution onto the first electrode as a mirror deposit, thereby affecting the reflectance of the REM device. An electrochemically stable surface modification layer deposited on the first electrode is usually required to facilitate substantially uniform nucleation of the electrodeposited metal in order to form a mirror deposit on the first elE~ctrode, such that the amount of deposited metal subsisting on the first electrode affects the reflectivity of the mii:ror for the radiation.
The reflectivity of this mirror can be selectively adjusted from near Oo to almost 100, depending on the amount of metal deposited on the conducting film. Conversely, when the polarity is reversed and a positive electrical potential is applied to the first electrode relative to the second electrode, the applied potential causes deposited metal to be dissolved from the first electrode and electrodeposited from the solution onto the second electrode, thereby reducing the reflectivity of the mirror.
In various embodiments, at least one of the electrodes and its substrate, are substantially transparent to at least a portion of the spectrum of electromagnetic WO 01/06312 PCT/USOOI1b858 iad~.arior.. For an adjustable reflectivity device, such as an automatically dimming mirror,~either the first electrode and substrate are made transparE:nt to enable adjustable reflectivity of light entering the device through the first electrode/substrate pane, or the second electrode and substrate are made transparent so 'that the radiation passes through the electrolyte to the mirror formed on the first electrode. The locally distributed electrode described in U.S. Patent 5,903,382 to Tench et al., which is assigned to the same assignee as the presentapplication, may be used to render the second electrode substantially transparent.
nor a device involving adjustable transmittance, such as a smart window, both electrodes are made substantia?ly transparent to the radiation, as described in U.S. Patent No. 5, 923, 456 to Tench et al. , also assigned to the same assignee as the present application.
The first electrode may be disposed uniformly on a first substrate, or may be disposed in a pattern. The surface modification layer may be a thin layer (i.e., sufficiently thin to be nominally transparent) of an finer:.
metal which is electrochemically more stable towards oxidation than the electrodeposited metal. An underlayer may be added between the first electrode and the surface modification layer to improve adhes ion.
The electrolytic solution of this invention provides improved stability, deposit quality, deposit erasure and cycle life performance. The solution contains a solvent, electrodepositable mirror metal cations, and halide and/or pseudohalide anions, with the total molar concentration ratio of halide and/or pseudohalide anions relative to the electrodepositable metal cations be~:ng more than a 6:1, and preferably greater than about 10: L. Halide/pseudohalide anions may be derived from one or more halide/pseudohalide compounds, as well as from any compound used to provide the electrodepositable mirror metal cat:ions. The electrolytic WO 01!06312 PCT/US00/16858 solution may include a gelling agent to form an aqueous or a .-ion-aaueous gel electrolyte.
Further features and advantages of the invention will be apparent to those skilled in th;e art from the following _ oetai-~.eG description, taken together with the accompanying draw;ng=.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross sectional view depicting a representative design of a reversible, electrochemical mirror (REM) device constructed according to the invention.
Figure 2 is a cross sectional view similar to Figure 1, but illustrating the configui:ation of the REM when sufficient negative electrical potential has been applied I5 to the first electrode relative to the second electrode to cause substantial quantities of trte metal to deposit onto the first electrode.
Figure 3 is a cross sectional view similar to Figures 1 and 2, but depicting the status of the REM when sufficient positive electrical potential has been applied to the first electrode relative to the second electrode to cause substantially all of the metal to deposit on the second electrode.
2~ 1~E'"Aii~ED DESCRIPTION OF THE INVENT:~,ON
Figure 1 is a cross sectional view depicting a representative design of a reversible electrochemical mirror (REM) constructed according to our invention (some dimensions, particularly layer thicknesses, are disproportionate in the drawings in order to more effectively illustrate the structure and function of the invention). The REM device in this example, which allows precise, reversible control over the reflection of electromagnetic radiation, includes a first substrate 102, which is substantially transparent to the portion of the spectrum of electromagnetic radiation which is to be controlled, and a second substrate 104. An electrically conducting film 106, which is also substantial~v transparent, is deposited on the first substrate. The film .. y06, with the optional addition of an electrochemically stable surface modification layer 108, functions as a first e.;.ectrode~ A second electrode :110 is deposited on the sewn; substrate 104. The second electrode can alternatively be a bulk electrode, a metal plate or sheet for example, with sufficient rigidity that the second substrate 104 would not be needeci. The second electrode 110 is electrochemically stable or is covered with a sufficient thickness of an active :metal layer 114 to avoid exposure of the second electrode surface. It may also be protected from exposure to the ele~~trolyte by a coating of electrochemically stable metal. The surface of electrode 110 may be roughened to reduce reflection of radiation from the electrode or to improve switching speed by lowering the current density.
An electrolytic solution II2 is located between and in a.iectr~cal contact with the electrodes 106 and 1I0.
Solution 112 contains a solvent, el.ectrodepositable mirror metal rations, and halide and/or ps~eudohalide anions, with the total molar concentration ratio of halide and/or pseudohalide anions relative to the electrodepositable metal rations being more than a~6:1. In the configuration depicted in Figure 1, the mirror may be initially charged by depositing the metallic layer 114 on the electrode IlO, i.e., the layer 114 is deposited on the electrode i10 prior to assembly of the REM cell. As those skilled in the art will appreciate, and as further explained in the discussion below regarding the operation of the REM, such a metallic layer may, alternatively, be initially deposited on the electrode 1I0, on the electrode 10E> ti. e., on the surface modification layer 108 as a layer 1a0?, or, as depicted in Figure I, divided between a p~artiai deposit on the electrode 106 and a partial deposit on the electrode 110.
If she electrode 110 is not itsel:E composed of the mirror metal, the amount of metal in these initially deposited 5 layers constitutes the maximum amount of metal which will be available for deposit, as explained in more detail ~ae~ow~ to control the reflectivity of the REM device.
Metal ions'116, which contain the same metal atoms as the layers 114 and 120, are dissolved within the electrolytic 1~,sclut~on 112 such that the metal atoms can be reversibly electrodeposited on and electrodissolved from the first and second electrodes. The surface modification layer 108 applied to the first electrode 106 facilitates the nucleation on this electrode of ele~;.trodeposited metal from the ions 116 to form a mirror depo~~it that highly reflects electromagnetic radiation.
The REM device is intended for use in conjunction with a source of electrical potential 118, which has a reversible polarity and adjustable or pre--set positive and negative potential values, connected between the first and second electrodes I06 and 110. When a negative electrical potential is applied to the first electrode 106 relative to the second electrode 110, metal 114 deposited on the second electrode 110 is dissolved from they second electrode into the electrolytic solution 112, while metal ions 116 in the solution are electrodeposited from the solution onto the surface modification layer 108 of tlae first electrode 106.
The surface modification layer 108 causes the metal to depos~.t in a substantially uniform .Layer, forming a mirror surface.
When the polarity of the applied potential is reversed, such that a positive potential is applied to the first electrode 106 relative to the second electrode IIO, deposited metal is dissolved from the first electrode into the solution 112 and dissolved metal will. is WO 01106312 PCTIUS00/1685$
electrodeposited from the solution onto the second °i°CtrOd~,.
The amount of deposited metal which remains on the first electrode determines the reflectivity which the mirror demonstrates for radiation. The process is reversible, and the mirror may be maintained at virtually any po~.nt between substantially complete deposition on and substantially complete erasure from the first electrode 106 without additional current being required. Thus the REM
mirror may be adjusted to any reflective value from approximately Oo reflective t:o approximately 1000 reflective. The lower limit of reflectivity for the REM
device is affected by the reflectivities of the nucleation layer 108, the electrode 106, and the substrate 102; these reflectivities may be reduced by use of anti-reflection.
coatings of the type commonlp emplcEyed, or by adjusting the layer thicknesses.
Figure 2 is a cross sectional. view similar to Figure 1, but illustrating the performance of the REM device when sufficient negative electrical potential has been applied to the first electrode relative to the second electrode for a sufficient period of time to cause a substantial layer of the metal to deposit onto the first electrode. In this condition, the layer 120, created by the deposited metal, 2~ functions as a highly reflective mirror and tends to reflect radiation, illustrated by tlhe light beam 122, which impinges on the mirror.
Figure 3 is a cross sectional view similar to Figures 1 and 2, but illustrating the behavior of the REM device when sufficient positive electrical potential has been applied to the first electrode relative to the second electrode for a sufficient period of time to cause substantially all of the electroactive metal to dissolve from the first electrode and to deposit as the metallic layer "4 on the second electrode. In this condition, the . WO 01/06312 PCT/US00/16858 . 12 REM imposes a minimal impediment: to incoming radiation, thereby allowing substantially all such incoming radiation of at least some wavelengths to be' transmitted through the first electrode 106 and surface modification layer 108 and .. r_c then be absorbed or dispersed by the electrolyte I12 or by the deposited metal 114 on the second electrode 1I0,. as illustrated by the light beam 124. Alternatively,. the transmitted light might be absorbed or dispersed by a gel ;natr;x if a gelled electrolyte is employed. An absorbing dye might also be added to the electrolyte to enhance light absorption. The second electrode 110 could also be a locally distributed electrode on a transparent substrate so that most of the radiation would pass through the device.
For the configuration depicted in Figure 3, the amount of reflected light is minimal.
In an alternative configuration, the first electrode can be disposed on a substrate that may be non-transparent, with the second electrode being essentially transparent and locally distributed on a transparent second substrate. In this variable reflectivity device, light entering through the second electrode and through the electrolyte can be reflected to varying degrees by the extent of mirror formation on the first electrode. The locally distributed electrode is described in U.S. Patent No. 5,923,456 to Tench et al. and assigned to the' same assignee as the present application.
The electrolytic solution 112 includes the following components:
I) a solvent. The solvent is preferably selected from the following group: dimethylsulfoxide (DMSO), ethylene glycol, propylene carbonate, dimethylformamide (DMF), gamma butyrolactone (GBL), water and mixtures of these solvents.
2) cations of an electrodepositable mirror metal(s).
The electrodepositable metals) is preferably selected from the following group: silver, bismuth., copper, tin, cadmium, _ WO 01106312 PCTIUS00116858 mercury, indium, lead, antimony, i~hallium and zinc.
Nishikitani et al. (European Patent No. 0,618,477) teaches that the counter electrode in electrochromic devices for smart window applications can be a metal grid which is substantially. transparernt. Since no metal electrodeposition occurs in el.ectrochromic devices, however, the grid in this case is used to provide a I5 transparent electrode, not to maintain transparency by localizing metal deposition. In addition, to provide adequate electrical capacity for electrochromic dev.~ces, Nishikitani's grid would need a very high surface area (at least 10 m~/g and preferably 50 to 5,000 m2/g) and a line width of 50 to 5,000 um; alternatively, a plurality of dots on a conducting substrate can be used, but the dots must contain fine particles having electrical capacitance of not less than 1 farad/g.
SUMMARY OF THE INVENTION
The reversible electrochemical mirror (REM) device of this invention permits efficient and precise control over the reflection of visible light and other electromagnetic radiation. The mirror device includes a first electrode, on which a mirror deposit is reversibly plated and dissolved, and a second electrode at which occurs the reverse of the metal piating/dissolution process occurring at the first electrode. At least one of the electrodes (and its substrate) is substantially transparent to at least a portion of the spectrum of electromaanetyc - WO 01!06312 PCT/US00/16858 radiation. Typically, the, transparent electrode is indium tin oxide (ITO) or fluorine doped t:in oxide (FTO) deposited or. a Transparent glass (or plastic? pane which serves as tine substrate. An electrolytic: solution .is disposed _ betweer. the first and second electrodes such that ions of a metal which can electrodeposit on these electrodes are soluble in the electrolytic solut:ion. The electrolytic solution described herein provides the inherent stability, high deposit quality, complete deposit erasure and long cycle life needed for practical applications.
When a negative electrical potential is applied to the first electrode relative to the second electrode, the applied potential causes deposited metal to be dissolved from the second electrode into the electrolytic solution and to be electrodeposited from the solution onto the first electrode as a mirror deposit, thereby affecting the reflectance of the REM device. An electrochemically stable surface modification layer deposited on the first electrode is usually required to facilitate substantially uniform nucleation of the electrodeposited metal in order to form a mirror deposit on the first elE~ctrode, such that the amount of deposited metal subsisting on the first electrode affects the reflectivity of the mii:ror for the radiation.
The reflectivity of this mirror can be selectively adjusted from near Oo to almost 100, depending on the amount of metal deposited on the conducting film. Conversely, when the polarity is reversed and a positive electrical potential is applied to the first electrode relative to the second electrode, the applied potential causes deposited metal to be dissolved from the first electrode and electrodeposited from the solution onto the second electrode, thereby reducing the reflectivity of the mirror.
In various embodiments, at least one of the electrodes and its substrate, are substantially transparent to at least a portion of the spectrum of electromagnetic WO 01/06312 PCT/USOOI1b858 iad~.arior.. For an adjustable reflectivity device, such as an automatically dimming mirror,~either the first electrode and substrate are made transparE:nt to enable adjustable reflectivity of light entering the device through the first electrode/substrate pane, or the second electrode and substrate are made transparent so 'that the radiation passes through the electrolyte to the mirror formed on the first electrode. The locally distributed electrode described in U.S. Patent 5,903,382 to Tench et al., which is assigned to the same assignee as the presentapplication, may be used to render the second electrode substantially transparent.
nor a device involving adjustable transmittance, such as a smart window, both electrodes are made substantia?ly transparent to the radiation, as described in U.S. Patent No. 5, 923, 456 to Tench et al. , also assigned to the same assignee as the present application.
The first electrode may be disposed uniformly on a first substrate, or may be disposed in a pattern. The surface modification layer may be a thin layer (i.e., sufficiently thin to be nominally transparent) of an finer:.
metal which is electrochemically more stable towards oxidation than the electrodeposited metal. An underlayer may be added between the first electrode and the surface modification layer to improve adhes ion.
The electrolytic solution of this invention provides improved stability, deposit quality, deposit erasure and cycle life performance. The solution contains a solvent, electrodepositable mirror metal cations, and halide and/or pseudohalide anions, with the total molar concentration ratio of halide and/or pseudohalide anions relative to the electrodepositable metal cations be~:ng more than a 6:1, and preferably greater than about 10: L. Halide/pseudohalide anions may be derived from one or more halide/pseudohalide compounds, as well as from any compound used to provide the electrodepositable mirror metal cat:ions. The electrolytic WO 01!06312 PCT/US00/16858 solution may include a gelling agent to form an aqueous or a .-ion-aaueous gel electrolyte.
Further features and advantages of the invention will be apparent to those skilled in th;e art from the following _ oetai-~.eG description, taken together with the accompanying draw;ng=.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross sectional view depicting a representative design of a reversible, electrochemical mirror (REM) device constructed according to the invention.
Figure 2 is a cross sectional view similar to Figure 1, but illustrating the configui:ation of the REM when sufficient negative electrical potential has been applied I5 to the first electrode relative to the second electrode to cause substantial quantities of trte metal to deposit onto the first electrode.
Figure 3 is a cross sectional view similar to Figures 1 and 2, but depicting the status of the REM when sufficient positive electrical potential has been applied to the first electrode relative to the second electrode to cause substantially all of the metal to deposit on the second electrode.
2~ 1~E'"Aii~ED DESCRIPTION OF THE INVENT:~,ON
Figure 1 is a cross sectional view depicting a representative design of a reversible electrochemical mirror (REM) constructed according to our invention (some dimensions, particularly layer thicknesses, are disproportionate in the drawings in order to more effectively illustrate the structure and function of the invention). The REM device in this example, which allows precise, reversible control over the reflection of electromagnetic radiation, includes a first substrate 102, which is substantially transparent to the portion of the spectrum of electromagnetic radiation which is to be controlled, and a second substrate 104. An electrically conducting film 106, which is also substantial~v transparent, is deposited on the first substrate. The film .. y06, with the optional addition of an electrochemically stable surface modification layer 108, functions as a first e.;.ectrode~ A second electrode :110 is deposited on the sewn; substrate 104. The second electrode can alternatively be a bulk electrode, a metal plate or sheet for example, with sufficient rigidity that the second substrate 104 would not be needeci. The second electrode 110 is electrochemically stable or is covered with a sufficient thickness of an active :metal layer 114 to avoid exposure of the second electrode surface. It may also be protected from exposure to the ele~~trolyte by a coating of electrochemically stable metal. The surface of electrode 110 may be roughened to reduce reflection of radiation from the electrode or to improve switching speed by lowering the current density.
An electrolytic solution II2 is located between and in a.iectr~cal contact with the electrodes 106 and 1I0.
Solution 112 contains a solvent, el.ectrodepositable mirror metal rations, and halide and/or ps~eudohalide anions, with the total molar concentration ratio of halide and/or pseudohalide anions relative to the electrodepositable metal rations being more than a~6:1. In the configuration depicted in Figure 1, the mirror may be initially charged by depositing the metallic layer 114 on the electrode IlO, i.e., the layer 114 is deposited on the electrode i10 prior to assembly of the REM cell. As those skilled in the art will appreciate, and as further explained in the discussion below regarding the operation of the REM, such a metallic layer may, alternatively, be initially deposited on the electrode 1I0, on the electrode 10E> ti. e., on the surface modification layer 108 as a layer 1a0?, or, as depicted in Figure I, divided between a p~artiai deposit on the electrode 106 and a partial deposit on the electrode 110.
If she electrode 110 is not itsel:E composed of the mirror metal, the amount of metal in these initially deposited 5 layers constitutes the maximum amount of metal which will be available for deposit, as explained in more detail ~ae~ow~ to control the reflectivity of the REM device.
Metal ions'116, which contain the same metal atoms as the layers 114 and 120, are dissolved within the electrolytic 1~,sclut~on 112 such that the metal atoms can be reversibly electrodeposited on and electrodissolved from the first and second electrodes. The surface modification layer 108 applied to the first electrode 106 facilitates the nucleation on this electrode of ele~;.trodeposited metal from the ions 116 to form a mirror depo~~it that highly reflects electromagnetic radiation.
The REM device is intended for use in conjunction with a source of electrical potential 118, which has a reversible polarity and adjustable or pre--set positive and negative potential values, connected between the first and second electrodes I06 and 110. When a negative electrical potential is applied to the first electrode 106 relative to the second electrode 110, metal 114 deposited on the second electrode 110 is dissolved from they second electrode into the electrolytic solution 112, while metal ions 116 in the solution are electrodeposited from the solution onto the surface modification layer 108 of tlae first electrode 106.
The surface modification layer 108 causes the metal to depos~.t in a substantially uniform .Layer, forming a mirror surface.
When the polarity of the applied potential is reversed, such that a positive potential is applied to the first electrode 106 relative to the second electrode IIO, deposited metal is dissolved from the first electrode into the solution 112 and dissolved metal will. is WO 01106312 PCTIUS00/1685$
electrodeposited from the solution onto the second °i°CtrOd~,.
The amount of deposited metal which remains on the first electrode determines the reflectivity which the mirror demonstrates for radiation. The process is reversible, and the mirror may be maintained at virtually any po~.nt between substantially complete deposition on and substantially complete erasure from the first electrode 106 without additional current being required. Thus the REM
mirror may be adjusted to any reflective value from approximately Oo reflective t:o approximately 1000 reflective. The lower limit of reflectivity for the REM
device is affected by the reflectivities of the nucleation layer 108, the electrode 106, and the substrate 102; these reflectivities may be reduced by use of anti-reflection.
coatings of the type commonlp emplcEyed, or by adjusting the layer thicknesses.
Figure 2 is a cross sectional. view similar to Figure 1, but illustrating the performance of the REM device when sufficient negative electrical potential has been applied to the first electrode relative to the second electrode for a sufficient period of time to cause a substantial layer of the metal to deposit onto the first electrode. In this condition, the layer 120, created by the deposited metal, 2~ functions as a highly reflective mirror and tends to reflect radiation, illustrated by tlhe light beam 122, which impinges on the mirror.
Figure 3 is a cross sectional view similar to Figures 1 and 2, but illustrating the behavior of the REM device when sufficient positive electrical potential has been applied to the first electrode relative to the second electrode for a sufficient period of time to cause substantially all of the electroactive metal to dissolve from the first electrode and to deposit as the metallic layer "4 on the second electrode. In this condition, the . WO 01/06312 PCT/US00/16858 . 12 REM imposes a minimal impediment: to incoming radiation, thereby allowing substantially all such incoming radiation of at least some wavelengths to be' transmitted through the first electrode 106 and surface modification layer 108 and .. r_c then be absorbed or dispersed by the electrolyte I12 or by the deposited metal 114 on the second electrode 1I0,. as illustrated by the light beam 124. Alternatively,. the transmitted light might be absorbed or dispersed by a gel ;natr;x if a gelled electrolyte is employed. An absorbing dye might also be added to the electrolyte to enhance light absorption. The second electrode 110 could also be a locally distributed electrode on a transparent substrate so that most of the radiation would pass through the device.
For the configuration depicted in Figure 3, the amount of reflected light is minimal.
In an alternative configuration, the first electrode can be disposed on a substrate that may be non-transparent, with the second electrode being essentially transparent and locally distributed on a transparent second substrate. In this variable reflectivity device, light entering through the second electrode and through the electrolyte can be reflected to varying degrees by the extent of mirror formation on the first electrode. The locally distributed electrode is described in U.S. Patent No. 5,923,456 to Tench et al. and assigned to the' same assignee as the present application.
The electrolytic solution 112 includes the following components:
I) a solvent. The solvent is preferably selected from the following group: dimethylsulfoxide (DMSO), ethylene glycol, propylene carbonate, dimethylformamide (DMF), gamma butyrolactone (GBL), water and mixtures of these solvents.
2) cations of an electrodepositable mirror metal(s).
The electrodepositable metals) is preferably selected from the following group: silver, bismuth., copper, tin, cadmium, _ WO 01106312 PCTIUS00116858 mercury, indium, lead, antimony, i~hallium and zinc.
3' at least one halide or pse~adohalide compound having a cat~or. that is not electroactive in the voltage range aver which the REM is operated. The halide/pseudohalide compounds; preferably includes a cation selected from the following group: lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, and hydrogen. -Alternatively, the hali~de/pseudohalide compound can be an alkylammonium halide/pseudohalide salt.
Halide/pseudohalide compounds) having a cation that is not electroactive is added to the solLxtion until the ratio of the total molar concentration of all halide/pseudohalide anions to the total molar concentration of all mirror metal cations is at least 6:~1; a ratio of at least 10:1 being preferred. Halide/pseudohalide anions may be derived from compounds comprising the mirror metal cations and canons that do not react electrochem:~cally under the REM
conditions employed. The mirror metal may be an alloy comprised of more than one metallic: element. In computing the halide/pseudohalide to mirror metal molar ratio,, the total concentrations of all halide/pseudohalide anions and all mirror metal ions is used.
The use of a higher halide,~pseudohalide anion to active metal cation molar concentration ratio as specified herein increases the degree to which the active metal ions are stabilized in the electrolyte ('via complexing with the halide/pseudohalide anions). The enhanced active metal ion stability increases the inherent stability of the solution against precipitation of the actives metal or an insoluble metal compound and raises the overvoltage for deposition of the metal. It also facilitates electrodissolution and inhibits passivation of the mirror metal deposit for faster and more complete erasure and greatly increased device cycle life. The higher overvoltagE= improves the deposit uniformity and mirror qualit y by increasing overall resistance to current flow (ao that variations in electrolyte resistive paths are less important), and by nh~bz~ing deposition at micro-peaks in the substrate that car. result in runaway dendritic deposit growth associated with the higher electric field prE:sent at such peaks.
A REM device as described herein, employing ar.
electrolyte having a halide/pseudohalide anion to active metal ion molar .concentration ratio of greater than 6:1, exhibited greater inherent electrolyte stability, enhanced mirror deposit quality, better erasure and longer cycle life when compared with devices using lower ratios, or which utilize other substances - such as organic additives - it their electrolyte formulations. A REM device was constructed employing a halide anion/silver ion molar I5 concentration ratio of 13:1 in a DMSO solvent, with no other additives, which provided high-quality mirror deposits for 100,000 cycles. Good results were also obtained with other solvents, e.g., ethylene glycol, water, and ethylene glycol/water mixtures.
Prior art efforts using lower ratios, or which use complicated electrolyte formulat_'Lons involving organic additives, have produced devices that are incapable of producing mirror-like deposits and/or which suffer from other performance problems. The novel technique described herein avoids the complications brought about by other approaches, and enables the straightforward fabrication of practical and reliable REM devices with long cycle life.
Fabrication of a Preferred EmbodimE~nt The preferred first electrode utilizes a glass or plastic substrate which is uniforrttly coated on one side with an optically transparent, low resistivity (about 10 S2/square) ITO (indium tin oxide) or FTO (fluorine-doped tin oxide) film. An optically thin adherent inert metal, such as Pt, is vapor deposited, preferably by sputtering, onto the ITO or FTO surface to enhance' the rate of nucleation fcr :petal deposition to yield a mirror deposit; other electrochemically inert metals can also be used, e.g..
gold, palladium, rhodium, iridium, ruthenium, rhenium, etc.
it may be advantageous in some cases to employ a duplex meta-.~ film, e.g., Ti/Au or Cr/Au, in which the very thin underiayer metal (e. g., Ti or Cr) serves to improve adhesion of the. noble metal nucleation layer to the substrate., This nucleation layer is not necessary for some _;
"' i~EN svwrems, notably aqueous silver cyanide electrolytes An electrical bus connection is formed around the perimeter of the ITO or FTO coating.
For REM devices involving adjustable transmittance, the preferred second electrode is locally distributed, as 15 described in U.S. Patent No. 5;903,382 to Tench et al., which is assigned to the same aasignee as the present application. In this case, the second electrode comprises a metal grid or nucleation layer matrix pattern of relatively small overall area so tlhat metal plated on the second electrode blocks only a small fraction of the radiation.
For adjustable reflectivity REM devices, the preferred second electrode includes a sheet: of the mirror metal (silver, for example) or of anothez: metal, which has been roughened (by bead blasting, for example) to reduce reflection of radiation from the second electrode. When the second electrode is not electrochemically stable under the operating conditions, an excess amount of mirror metal is used so that the second electrode is always covered with the mirror metal and is not exposed to the solution.
Alternatively, a protective layer of an electrochemically inert metal, such as platinum, is used between the reactive substrate and the mirror metal. Prior to cell assembly, the second electrode, if other than the mirror metal, is '35 plated with a quantity of mirror metal sufficient to WO O1I06312 PCT/US00/1b858 provide the desired amount of reflectivity when deposited on the first electrode and to prevent exposure of the second electrode substrate metal to the electrolyte.
(Alternatively, the first electrode can be plated with the :n~. Yr~ci metal ; .
The preferred electrolyte is ,s gelled electrolyte that is both chemically and electrochemically stable except with regard to~ electrodeposition c~f the mirror metal.
Preferably, the mirror metal is silver added to the 1C; electrolyte as a silver halide or pseudohalide and stab~.l izea ~n the electrolyte by <addition of an excess of na.~yae~nseudohalide ions derived from addition of a compound having a cation that is not electroactive (e. g., lithium, sodium or potassium), with the resulting 15 halide/pseudohalide anion to silver ion molar concentration ratio being at least 6:l as descr~.bed above. Other mirror metals having relatively low toxicity and good electrochemical characteristics include copper, tin, and bismuth. A mixture of halide/pseudohalide ions (chloride, 20 iodide, bromide, cyanide and thiocyanate) may be employed.
The solvent is chosen with respect to its freezing and boiling point to provide the desirs;d temperature operating range, as well as good electrolyte stability and good mirror cycling characteristics. Pre ferred solvents include 25 water, dimethylsulfoxide (DMSO), ethylene glycol, gamma -butyrolactone (GBL), dimethylformamide (DMF) and mixtures of these. Solubility considerations may limit the acceptable combinations of mirror metal salts, halide/pseudohalide compounds and solvents. Additives that 30 are electroactive or decomposed dur~.ng electrodeposition of the mirror metal, such as organic compounds normally used for leveling and brightening electrodeposits, should be avoided since they would limit the device cycle life.
Although the REM of this invention can be fabricated 35 using a liquid electrolyte, use of an electrolyte stiffener 1.7 is preferred to facilitate mirror fabrication, to minimize electrolyte loss that may affect mirror performance or create a chemical safety hazard; and to adhesively hold glass fragments formed during accidental breakage that could otherwise cause physical personal injury. Preferred electrolyte stiffeners include organic gelling agents, e.g.. polyacrylonitrile (PAN), polyvinylalcohol (PVA;, poiyvinylac~etate. (PVOAc), and polymethylmethacryiate (PMMA), which dissolve in liquidl electrolytes to form transparent plastic-like gels at ambient temperatures.
With an appropriate amount of gelling agent, the electrolyte can retain much of the conductivity of the liquid electrolyte; yet be cut and applied as a "solid state" component. The specific organic polymer gelling 1.5 agent is chosen based on gel stability and chemical and electrochemical compatibility with .a given electrolyte and the metal mirror formation/erasure processes. Other possible electrolyte stiffeners include porous solid polymers that absorb large quantities of electrolyte, e.g., ormasils and porous polypropylene. In some cases, the solid polymer matrix may be formed by in situ polymerization of monomers dissolved in the electrolyte.
The reversible electrochemical cells of this invention can be fabricated using spacers and. a polymer sealant, or using a gasket or o-ring to provide iboth the proper spacing and a seal. The spacer and seal materials must be chemically compatible with the electrolyte. Good results have been obtained with polypropylene spacers and silicone sealants. The preferred electrode separation is about 0.05 - 3.0 mm. Electrical contact is made to the metal bus on each electrode and connected to a voltage source for switching.
Examvles J5 Z. An ad;ustable reflectivity REM cell having a viewina area of 7.6 x 12.7 cm was constructed using a mirror e~.~ect=octe comprised of a 30 A sputtered platinum Nucleation layer on ~.1 ohm/s~quare FTO film on a glass substrate. The counter eie~ctrode was a 25um thick silver foil (99.99% purity) that had been roughened by bead blasting (170 grit) and was mechanically supported by a thick plast;ic backing plate. The electrolyte~was 0.15 M AgI + 1.8 M LiCl (halide/silver molar concentration ratio of 13.0) in a DMSO solvent..
i~: A polypropylene frame providled a 2.4 mm cell spacing ane 3 silicone o-ring provided a seal. This cell exhibited excellent mirror formation and erasure during deep cycling between -0.5 V (relative to the mirror electrode) for 25 s and +0.25 V for 65 s for 46,000 cycles. Mirror formation remained practically uniformo although redistribution of the counter electrode silver resulting in exposure of the backing plate was eventually observed. Separate experiments showed that exclusion of oxygen from the electrolyte is necessary to avoid chemical dissolution of silver metal that can cause mirror loss on open circuit and possibly contribute to silver metal redistribution.
2. An adjustable reflectivity R1EM cell having a viewing area of 7.6 x 12.7 cm was constructed using a mirror electrode comprised of a 30 ~1 sputtered platinum nucleation layer on i1 ohm/square FTO film on a glass substrate. The counter electrode was 25um thick silver electrodeposited from <~ commercial plating bath on a copper plate that had been roughened by sanding (400 ctrit). Cell fabrication procedures and the electrolyte were the same as f:or Example 1. This cell also exhibited excellent mirror formation and erasure and was cycled between -0.4 V for 25 s and +0.25 V for 65 s for 100,000 cycles without sicrnificant degradation in the mirror quality.
3. The following electrolytic solutions also provided highly reversible mirror p.lating/erasure on noble _ meta? nucleation layers on 10 ohms/square ITO or. glass subs ti a tes A. 3 M sodium iodide with 0.15 M silver iodide in water .with a 60A Pt/ITO electrode (halide ion/silver ion molar concentration ratio of 21).
B. 1.8 M sodium iodide with 0.15 M silver iodide in ?5~ ethylene glycol in water with a 60A Pt/ITO
electrode (halide ion/silver ion molar concentration ratio of 13).
C. 1.8 M sodium iodide with 0.15M silver iodide in I5 100°s ethylene glycol with a 60A Pt/ITO electrode (halide ion/silver ion molar concentration ratio of 13).
D. 10.6 M sodium thiocyanate with 0.34 M silver perchlorate in water adjusted to pH 2.2 with 0.2 M tartaric acid with a 60A Ti/Au/ITO electrode (pseudohalide ion/silve:r ion molar ratio of 31.2).
Features of the Invention To attain the uniform metal deposition needed for mirror-like reflectivity, it is~usually necessary to treat the transparent conducting film of the first electrode to improve nucleation, e.g., by vapor deposition of a very thin, yet optically transparent (~1.'i-200 A) "seed" layer of a metal (e. g., platinum or gold) that is electrochemically inert over the operating voltage range of the device. This seed layer enhances the rate of nucleation so that mirror deposits are obtained. Other surface treatments (e. g., electrodeposition of an inert metal layer) could be used to improve metal nucleation and provide mirror deposits. In WO 01!06312 PCT/US00/16858 _ 20 order to be effective for. producing mirror deposits, the nucleation layer must be microscop~~cally continuous, which may not be the case for some metallization treatments on some transparent conductor substrates. For example, the two-step process commonly used to metallize printed wiring boards prior to copper plating (involving palladium displacement of adsorbed. tin ions) may not produce suff~cien~i:y continuous films with adequate adhesion. Fcr special effects, e.g., a decorative mirror design; the i0 transparent conductor (e. g., ITO o:r FTO) and/or the metal nucleation layer can be patterned as desired.
The electrolyte of this invention employs a relatively high molar concentration ratio of halide or pseudohalide anions to active metal cations (more than 6:1) in order to stabilize the electrolyte, improve mirror deposit quality, facilitate complete erasure, and improve device cycle life.
This eliminates the need for other complexing agents or additives that may themselves be unstable during long-term cycling of the device. In some cares, however, it may be advantageous to use augmenting electrochemically stable additives that further inhibit the metal deposition process by complexing the mirror metal ions or adsorbing on the electrode surface. Most of the organic addition agents used in the plating industry to brighten and level deposits, however, are electrochem:i.cally consumed during the metal deposition process avd would be inappropriate.
For some systems, e.g., aqueous silver cyanide, mirror deposits may be obtained without the use of a noble metal nucleation layer.
No chemically reactive species are produced, since the same metal deposition/dissolution reaction occurs at both electrodes. As a result, a particular switched state is maintained indefinitely at open circuit if oxidizing contaminants are excluded from the cell.
The REM device of this invention is an eiectroreflective device, !light reflection changed by application of voltage), rather than an electrochromic device :light absorption changed by applied voltage) as is ~ypicai of the devices taught i.n the prior art. REM
devices can be designed to modulate reflectance and/or transmission of light.
The REM is operated well wii:hin the electrolyte and e-.~ectroae;riucieation layer stability regions, se that excessive metal plating or depiatin.g is not harmful. In iG fact. the REM is always self-limiting for erasure of the mirror electrode when biased with:Ln the voltage stability region, since the current will practically cease when the deposited metal is depleted from that electrode. By limiting the amount of mirror metal deposited on the second i5 electrode prior to cell assembly, cwerplating of the first electrode under a protracted applied voltage can also be precluded.
No cell separator is required, since the same redox couple reaction !metal deposition/dissolution? involving a 20 solid product takes place at both electrodes, so that side reactions are avoided. On the other hahd, a porous cell separator, e.g., porous polypropylene, may be used to provide a matrix for containing a liquid electrolyte and to prevent shorting of the two electrodes in the event of 25 extreme flexure of the cell.
A wide temperature operating range is obtained by using electrolytes based on high boiling organic solvents, e.g., dimethylsulfoxide, ethylene glycol; propylene carbonate, y-butyrolactone, etc. Use of mixtures of these 30 solvents can extend the temperature range to lower operating temperatures.
Use of a "solid state" gel electrolyte which incorporates an electrochemically inert polymer stiffener facilitates mirror fabrication, minimizes the possibility 35 of chemical or physica l personal injury, and reduces sensitivity tc ceil leakage and atmospheric contamination by preventing convectional transport (diffusion is a very slow proCessi.
The preferred embodiments of 'this invention have been illustrated and described above'. Modifications and 3dd~tiona~. embodiments, however, will undoubtedly be apparent to those skilled in the art. Furthermore, equivalent elements may be ~~ubstituted for those illustrated and described herein" parts or connections i0 might be reversed or otherwise interchanged, and certain features of the invention may be utilized independently of other features. Consequently; the= exemplary embodiments should be considered illustrative, rather than inclusive, while the appended claims are more indicative of the full 15 scope of the invention.
Halide/pseudohalide compounds) having a cation that is not electroactive is added to the solLxtion until the ratio of the total molar concentration of all halide/pseudohalide anions to the total molar concentration of all mirror metal cations is at least 6:~1; a ratio of at least 10:1 being preferred. Halide/pseudohalide anions may be derived from compounds comprising the mirror metal cations and canons that do not react electrochem:~cally under the REM
conditions employed. The mirror metal may be an alloy comprised of more than one metallic: element. In computing the halide/pseudohalide to mirror metal molar ratio,, the total concentrations of all halide/pseudohalide anions and all mirror metal ions is used.
The use of a higher halide,~pseudohalide anion to active metal cation molar concentration ratio as specified herein increases the degree to which the active metal ions are stabilized in the electrolyte ('via complexing with the halide/pseudohalide anions). The enhanced active metal ion stability increases the inherent stability of the solution against precipitation of the actives metal or an insoluble metal compound and raises the overvoltage for deposition of the metal. It also facilitates electrodissolution and inhibits passivation of the mirror metal deposit for faster and more complete erasure and greatly increased device cycle life. The higher overvoltagE= improves the deposit uniformity and mirror qualit y by increasing overall resistance to current flow (ao that variations in electrolyte resistive paths are less important), and by nh~bz~ing deposition at micro-peaks in the substrate that car. result in runaway dendritic deposit growth associated with the higher electric field prE:sent at such peaks.
A REM device as described herein, employing ar.
electrolyte having a halide/pseudohalide anion to active metal ion molar .concentration ratio of greater than 6:1, exhibited greater inherent electrolyte stability, enhanced mirror deposit quality, better erasure and longer cycle life when compared with devices using lower ratios, or which utilize other substances - such as organic additives - it their electrolyte formulations. A REM device was constructed employing a halide anion/silver ion molar I5 concentration ratio of 13:1 in a DMSO solvent, with no other additives, which provided high-quality mirror deposits for 100,000 cycles. Good results were also obtained with other solvents, e.g., ethylene glycol, water, and ethylene glycol/water mixtures.
Prior art efforts using lower ratios, or which use complicated electrolyte formulat_'Lons involving organic additives, have produced devices that are incapable of producing mirror-like deposits and/or which suffer from other performance problems. The novel technique described herein avoids the complications brought about by other approaches, and enables the straightforward fabrication of practical and reliable REM devices with long cycle life.
Fabrication of a Preferred EmbodimE~nt The preferred first electrode utilizes a glass or plastic substrate which is uniforrttly coated on one side with an optically transparent, low resistivity (about 10 S2/square) ITO (indium tin oxide) or FTO (fluorine-doped tin oxide) film. An optically thin adherent inert metal, such as Pt, is vapor deposited, preferably by sputtering, onto the ITO or FTO surface to enhance' the rate of nucleation fcr :petal deposition to yield a mirror deposit; other electrochemically inert metals can also be used, e.g..
gold, palladium, rhodium, iridium, ruthenium, rhenium, etc.
it may be advantageous in some cases to employ a duplex meta-.~ film, e.g., Ti/Au or Cr/Au, in which the very thin underiayer metal (e. g., Ti or Cr) serves to improve adhesion of the. noble metal nucleation layer to the substrate., This nucleation layer is not necessary for some _;
"' i~EN svwrems, notably aqueous silver cyanide electrolytes An electrical bus connection is formed around the perimeter of the ITO or FTO coating.
For REM devices involving adjustable transmittance, the preferred second electrode is locally distributed, as 15 described in U.S. Patent No. 5;903,382 to Tench et al., which is assigned to the same aasignee as the present application. In this case, the second electrode comprises a metal grid or nucleation layer matrix pattern of relatively small overall area so tlhat metal plated on the second electrode blocks only a small fraction of the radiation.
For adjustable reflectivity REM devices, the preferred second electrode includes a sheet: of the mirror metal (silver, for example) or of anothez: metal, which has been roughened (by bead blasting, for example) to reduce reflection of radiation from the second electrode. When the second electrode is not electrochemically stable under the operating conditions, an excess amount of mirror metal is used so that the second electrode is always covered with the mirror metal and is not exposed to the solution.
Alternatively, a protective layer of an electrochemically inert metal, such as platinum, is used between the reactive substrate and the mirror metal. Prior to cell assembly, the second electrode, if other than the mirror metal, is '35 plated with a quantity of mirror metal sufficient to WO O1I06312 PCT/US00/1b858 provide the desired amount of reflectivity when deposited on the first electrode and to prevent exposure of the second electrode substrate metal to the electrolyte.
(Alternatively, the first electrode can be plated with the :n~. Yr~ci metal ; .
The preferred electrolyte is ,s gelled electrolyte that is both chemically and electrochemically stable except with regard to~ electrodeposition c~f the mirror metal.
Preferably, the mirror metal is silver added to the 1C; electrolyte as a silver halide or pseudohalide and stab~.l izea ~n the electrolyte by <addition of an excess of na.~yae~nseudohalide ions derived from addition of a compound having a cation that is not electroactive (e. g., lithium, sodium or potassium), with the resulting 15 halide/pseudohalide anion to silver ion molar concentration ratio being at least 6:l as descr~.bed above. Other mirror metals having relatively low toxicity and good electrochemical characteristics include copper, tin, and bismuth. A mixture of halide/pseudohalide ions (chloride, 20 iodide, bromide, cyanide and thiocyanate) may be employed.
The solvent is chosen with respect to its freezing and boiling point to provide the desirs;d temperature operating range, as well as good electrolyte stability and good mirror cycling characteristics. Pre ferred solvents include 25 water, dimethylsulfoxide (DMSO), ethylene glycol, gamma -butyrolactone (GBL), dimethylformamide (DMF) and mixtures of these. Solubility considerations may limit the acceptable combinations of mirror metal salts, halide/pseudohalide compounds and solvents. Additives that 30 are electroactive or decomposed dur~.ng electrodeposition of the mirror metal, such as organic compounds normally used for leveling and brightening electrodeposits, should be avoided since they would limit the device cycle life.
Although the REM of this invention can be fabricated 35 using a liquid electrolyte, use of an electrolyte stiffener 1.7 is preferred to facilitate mirror fabrication, to minimize electrolyte loss that may affect mirror performance or create a chemical safety hazard; and to adhesively hold glass fragments formed during accidental breakage that could otherwise cause physical personal injury. Preferred electrolyte stiffeners include organic gelling agents, e.g.. polyacrylonitrile (PAN), polyvinylalcohol (PVA;, poiyvinylac~etate. (PVOAc), and polymethylmethacryiate (PMMA), which dissolve in liquidl electrolytes to form transparent plastic-like gels at ambient temperatures.
With an appropriate amount of gelling agent, the electrolyte can retain much of the conductivity of the liquid electrolyte; yet be cut and applied as a "solid state" component. The specific organic polymer gelling 1.5 agent is chosen based on gel stability and chemical and electrochemical compatibility with .a given electrolyte and the metal mirror formation/erasure processes. Other possible electrolyte stiffeners include porous solid polymers that absorb large quantities of electrolyte, e.g., ormasils and porous polypropylene. In some cases, the solid polymer matrix may be formed by in situ polymerization of monomers dissolved in the electrolyte.
The reversible electrochemical cells of this invention can be fabricated using spacers and. a polymer sealant, or using a gasket or o-ring to provide iboth the proper spacing and a seal. The spacer and seal materials must be chemically compatible with the electrolyte. Good results have been obtained with polypropylene spacers and silicone sealants. The preferred electrode separation is about 0.05 - 3.0 mm. Electrical contact is made to the metal bus on each electrode and connected to a voltage source for switching.
Examvles J5 Z. An ad;ustable reflectivity REM cell having a viewina area of 7.6 x 12.7 cm was constructed using a mirror e~.~ect=octe comprised of a 30 A sputtered platinum Nucleation layer on ~.1 ohm/s~quare FTO film on a glass substrate. The counter eie~ctrode was a 25um thick silver foil (99.99% purity) that had been roughened by bead blasting (170 grit) and was mechanically supported by a thick plast;ic backing plate. The electrolyte~was 0.15 M AgI + 1.8 M LiCl (halide/silver molar concentration ratio of 13.0) in a DMSO solvent..
i~: A polypropylene frame providled a 2.4 mm cell spacing ane 3 silicone o-ring provided a seal. This cell exhibited excellent mirror formation and erasure during deep cycling between -0.5 V (relative to the mirror electrode) for 25 s and +0.25 V for 65 s for 46,000 cycles. Mirror formation remained practically uniformo although redistribution of the counter electrode silver resulting in exposure of the backing plate was eventually observed. Separate experiments showed that exclusion of oxygen from the electrolyte is necessary to avoid chemical dissolution of silver metal that can cause mirror loss on open circuit and possibly contribute to silver metal redistribution.
2. An adjustable reflectivity R1EM cell having a viewing area of 7.6 x 12.7 cm was constructed using a mirror electrode comprised of a 30 ~1 sputtered platinum nucleation layer on i1 ohm/square FTO film on a glass substrate. The counter electrode was 25um thick silver electrodeposited from <~ commercial plating bath on a copper plate that had been roughened by sanding (400 ctrit). Cell fabrication procedures and the electrolyte were the same as f:or Example 1. This cell also exhibited excellent mirror formation and erasure and was cycled between -0.4 V for 25 s and +0.25 V for 65 s for 100,000 cycles without sicrnificant degradation in the mirror quality.
3. The following electrolytic solutions also provided highly reversible mirror p.lating/erasure on noble _ meta? nucleation layers on 10 ohms/square ITO or. glass subs ti a tes A. 3 M sodium iodide with 0.15 M silver iodide in water .with a 60A Pt/ITO electrode (halide ion/silver ion molar concentration ratio of 21).
B. 1.8 M sodium iodide with 0.15 M silver iodide in ?5~ ethylene glycol in water with a 60A Pt/ITO
electrode (halide ion/silver ion molar concentration ratio of 13).
C. 1.8 M sodium iodide with 0.15M silver iodide in I5 100°s ethylene glycol with a 60A Pt/ITO electrode (halide ion/silver ion molar concentration ratio of 13).
D. 10.6 M sodium thiocyanate with 0.34 M silver perchlorate in water adjusted to pH 2.2 with 0.2 M tartaric acid with a 60A Ti/Au/ITO electrode (pseudohalide ion/silve:r ion molar ratio of 31.2).
Features of the Invention To attain the uniform metal deposition needed for mirror-like reflectivity, it is~usually necessary to treat the transparent conducting film of the first electrode to improve nucleation, e.g., by vapor deposition of a very thin, yet optically transparent (~1.'i-200 A) "seed" layer of a metal (e. g., platinum or gold) that is electrochemically inert over the operating voltage range of the device. This seed layer enhances the rate of nucleation so that mirror deposits are obtained. Other surface treatments (e. g., electrodeposition of an inert metal layer) could be used to improve metal nucleation and provide mirror deposits. In WO 01!06312 PCT/US00/16858 _ 20 order to be effective for. producing mirror deposits, the nucleation layer must be microscop~~cally continuous, which may not be the case for some metallization treatments on some transparent conductor substrates. For example, the two-step process commonly used to metallize printed wiring boards prior to copper plating (involving palladium displacement of adsorbed. tin ions) may not produce suff~cien~i:y continuous films with adequate adhesion. Fcr special effects, e.g., a decorative mirror design; the i0 transparent conductor (e. g., ITO o:r FTO) and/or the metal nucleation layer can be patterned as desired.
The electrolyte of this invention employs a relatively high molar concentration ratio of halide or pseudohalide anions to active metal cations (more than 6:1) in order to stabilize the electrolyte, improve mirror deposit quality, facilitate complete erasure, and improve device cycle life.
This eliminates the need for other complexing agents or additives that may themselves be unstable during long-term cycling of the device. In some cares, however, it may be advantageous to use augmenting electrochemically stable additives that further inhibit the metal deposition process by complexing the mirror metal ions or adsorbing on the electrode surface. Most of the organic addition agents used in the plating industry to brighten and level deposits, however, are electrochem:i.cally consumed during the metal deposition process avd would be inappropriate.
For some systems, e.g., aqueous silver cyanide, mirror deposits may be obtained without the use of a noble metal nucleation layer.
No chemically reactive species are produced, since the same metal deposition/dissolution reaction occurs at both electrodes. As a result, a particular switched state is maintained indefinitely at open circuit if oxidizing contaminants are excluded from the cell.
The REM device of this invention is an eiectroreflective device, !light reflection changed by application of voltage), rather than an electrochromic device :light absorption changed by applied voltage) as is ~ypicai of the devices taught i.n the prior art. REM
devices can be designed to modulate reflectance and/or transmission of light.
The REM is operated well wii:hin the electrolyte and e-.~ectroae;riucieation layer stability regions, se that excessive metal plating or depiatin.g is not harmful. In iG fact. the REM is always self-limiting for erasure of the mirror electrode when biased with:Ln the voltage stability region, since the current will practically cease when the deposited metal is depleted from that electrode. By limiting the amount of mirror metal deposited on the second i5 electrode prior to cell assembly, cwerplating of the first electrode under a protracted applied voltage can also be precluded.
No cell separator is required, since the same redox couple reaction !metal deposition/dissolution? involving a 20 solid product takes place at both electrodes, so that side reactions are avoided. On the other hahd, a porous cell separator, e.g., porous polypropylene, may be used to provide a matrix for containing a liquid electrolyte and to prevent shorting of the two electrodes in the event of 25 extreme flexure of the cell.
A wide temperature operating range is obtained by using electrolytes based on high boiling organic solvents, e.g., dimethylsulfoxide, ethylene glycol; propylene carbonate, y-butyrolactone, etc. Use of mixtures of these 30 solvents can extend the temperature range to lower operating temperatures.
Use of a "solid state" gel electrolyte which incorporates an electrochemically inert polymer stiffener facilitates mirror fabrication, minimizes the possibility 35 of chemical or physica l personal injury, and reduces sensitivity tc ceil leakage and atmospheric contamination by preventing convectional transport (diffusion is a very slow proCessi.
The preferred embodiments of 'this invention have been illustrated and described above'. Modifications and 3dd~tiona~. embodiments, however, will undoubtedly be apparent to those skilled in the art. Furthermore, equivalent elements may be ~~ubstituted for those illustrated and described herein" parts or connections i0 might be reversed or otherwise interchanged, and certain features of the invention may be utilized independently of other features. Consequently; the= exemplary embodiments should be considered illustrative, rather than inclusive, while the appended claims are more indicative of the full 15 scope of the invention.
Claims (10)
1. A reversible electrochemical mirror device for controlling the reflection of electromagnetic radiation, comprising:
a first electrode (106) ;
a second electrode (110), at least one of said first and second electrodes being substantially transparent to at least a portion of the spectrum of electromagnetic radiation;
an electrolytic solution (112) disposed between and in electrical contact with the first and second electrodes, said electrolytic solution comprising:
a solvent , a source of cations of at least one electrodepositable mirror metal, at least one halide or pseudohalide compound having cations that are not electroactive in the voltage range over which the device is operated, the ratio of the total molar concentration of halide/pseudohalide anions (where said total is the aggregate of anions originating from said halide/pseudohalide compound and anions originating from said source of said electrodepositable mirror metal cations) to the total molar concentration of said electrodepositable mirror metal cations being greater than 6:1; and a plurality of atoms (114) of said electrodepositable mirror metal disposed on either the first or the second electrode, such that a negative electrical potential applied to the first electrode relative to the second electrode tends to cause deposited metal to be dissolved from the second electrode into the solution and to be electrodeposited from the solution as a mirror deposit onto the first electrode, and such that a positive electrical potential applied to the first electrode relative to the second electrode tends to cause deposited metal to be dissolved from the first electrode into the solution and electrodeposited from the solution onto the second electrode, the amount of deposited metal subsisting on the first electrode affecting the reflection of electromagnetic radiation by the device.
a first electrode (106) ;
a second electrode (110), at least one of said first and second electrodes being substantially transparent to at least a portion of the spectrum of electromagnetic radiation;
an electrolytic solution (112) disposed between and in electrical contact with the first and second electrodes, said electrolytic solution comprising:
a solvent , a source of cations of at least one electrodepositable mirror metal, at least one halide or pseudohalide compound having cations that are not electroactive in the voltage range over which the device is operated, the ratio of the total molar concentration of halide/pseudohalide anions (where said total is the aggregate of anions originating from said halide/pseudohalide compound and anions originating from said source of said electrodepositable mirror metal cations) to the total molar concentration of said electrodepositable mirror metal cations being greater than 6:1; and a plurality of atoms (114) of said electrodepositable mirror metal disposed on either the first or the second electrode, such that a negative electrical potential applied to the first electrode relative to the second electrode tends to cause deposited metal to be dissolved from the second electrode into the solution and to be electrodeposited from the solution as a mirror deposit onto the first electrode, and such that a positive electrical potential applied to the first electrode relative to the second electrode tends to cause deposited metal to be dissolved from the first electrode into the solution and electrodeposited from the solution onto the second electrode, the amount of deposited metal subsisting on the first electrode affecting the reflection of electromagnetic radiation by the device.
2. The device of claim 1, wherein said first electrode is substantially transparent to at least a portion of the spectrum of electromagnetic radiation, further comprising a first substrate (102) which is substantially transparent to at least a portion of the spectrum of electromagnetic radiation, the first electrode being disposed on the first substrate.
3. The device of claim 1, further comprising a surface modification layer (108) on the first electrode.
4. The device of claim 1, wherein said second electrode is substantially transparent to at least a portion of the spectrum of electromagnetic radiation, further comprising a second substrate (104) which is substantially transparent to at least a portion of the spectrum of electromagnetic radiation, the second electrode being disposed on the second substrate.
5. The device of claim 4, wherein the second electrode is a locally distributed electrode.
6. The device of claim 1, wherein said second electrode is a continuous electrical conductor, further comprising a second substrate (104) which is electrically insulating, the second electrode being deposited on the second substrate.
7. The device of claim 6, further comprising an underlayer between the second electrode and the second substrate to improve adhesion between the second electrode and the second substrate.
8. The device of claim 2, wherein the first electrode is disposed uniformly on the first substrate.
9. The device of claim 2, wherein the first electrode is disposed in a pattern on the first substrate.
10. The device of claim 1, wherein the total molar concentration ratio of halide/pseudohalide anions to the total molar concentration of said electrodepositable mirror metal cations is at least 10:1.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US09/356,730 US6111685A (en) | 1997-12-19 | 1999-07-19 | Reversible electrochemical mirror (REM) with improved electrolytic solution |
| US09/356,730 | 1999-07-19 | ||
| PCT/US2000/016858 WO2001006312A1 (en) | 1999-07-19 | 2000-06-20 | Reversible electrochemical mirror (rem) with improved electrolytic solution |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2340083A1 CA2340083A1 (en) | 2001-01-25 |
| CA2340083C true CA2340083C (en) | 2003-12-09 |
Family
ID=23402707
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002340083A Expired - Fee Related CA2340083C (en) | 1999-07-19 | 2000-06-20 | Reversible electrochemical mirror (rem) with improved electrolytic solution |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US6111685A (en) |
| EP (1) | EP1114354A4 (en) |
| JP (1) | JP2003505722A (en) |
| KR (1) | KR20010073166A (en) |
| BR (1) | BR0006947A (en) |
| CA (1) | CA2340083C (en) |
| WO (1) | WO2001006312A1 (en) |
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-
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- 1999-07-19 US US09/356,730 patent/US6111685A/en not_active Expired - Lifetime
-
2000
- 2000-06-20 JP JP2001510889A patent/JP2003505722A/en not_active Withdrawn
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- 2000-06-20 EP EP00942944A patent/EP1114354A4/en not_active Withdrawn
- 2000-06-20 CA CA002340083A patent/CA2340083C/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| KR20010073166A (en) | 2001-07-31 |
| WO2001006312A1 (en) | 2001-01-25 |
| CA2340083A1 (en) | 2001-01-25 |
| EP1114354A1 (en) | 2001-07-11 |
| JP2003505722A (en) | 2003-02-12 |
| US6111685A (en) | 2000-08-29 |
| BR0006947A (en) | 2001-07-31 |
| EP1114354A4 (en) | 2003-07-02 |
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