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Electrochromic Devices Comprising Metal Salts in an Ion Conductive Material

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Electrochromic Devices Comprising Metal Salts in an Ion Conductive Material Europaisches Patentamt 3 European Patent Office 00 Publication number: 0 392 694 Office europeen des brevets A2 EUROPEAN PATENT APPLICATION © Application number: 90303233.2 © int. Ci.5: G02F 1/17 @ Date of filing: 27.03.90 ® Priority: 14.04.89 US 338261 © Applicant: FORD MOTOR COMPANY LIMITED Eagle Way © Date of publication of application: Brentwood Essex(GB) 17.10.90 Bulletin 90/42 © GB © Designated Contracting States: Applicant: FORD FRANCE S. A. DE FR GB B.P. 307 F-92506 Rueil-Malmaison Cedex(FR) © FR Applicant: FORD-WERKE AKTIENGESELLSCHAFT Werk Kb'ln-Niehl Henry-Ford-Strasse Postfach 60 40 02 D-5000 Koln 60(DE) © DE @ Inventor: Demiryont, Hulya 7259 Appoline Dearborn, Michigan 48126(US) © Representative: Messulam, Alec Moses et al A. Messulam & Co. 24 Broadway Leigh on Sea Essex SS9 1BN(GB) © Electrochromic devices comprising metal salts in an ion conductive material. © This invention is directed to an electrochromic metal salts and an ion conduction enhancer in an ion device which comprises a colorable electrochromic conductive material. matrix layer (40) consisting essentially of certain CM < 3C> ^- O> o COPPER CO 36' ' CHLORIDE 6 • o • o • O • o ju v\> dJU 6 o o . CM Oo O •O'0'lol'<)o0t!'c;»o» 40- O» o • Oo0o0|.o0.0o00.0o O> 0»O •0»0*'o»o«oo»o oe.o.o Ca|oOoOoO.Q 34- 3Z V/////A 30^ a. Ill FIG.2 Xerox Copy Centre EP 0 392 694 A2 ELECTROCHROMIC DEVICES COMPRISING METAL SALTS IN AN ION CONDUCTIVE MATERIAL The present invention relates to electrochromic 4,652,090; 4,505,021 ; and 4,664,934. devices which exhibit coloration and bleaching In such devices, the electrochromic film usually thereof due to an induced electric field. More par- comprises an inorganic metal oxide material, most ticularly, this invention relates to electrochromic commonly a transition metal oxide, in particular: devices which include a layer comprising metal 5 tungsten oxide. When tungsten oxide is the elec- salts dispersed or dissolved in an ion conductive trochromic material, the electrolyte layer is adapted material. Herein this layer is termed an to provide a positively charged light cation, prefer- "electrochromic matrix material layer". ably, a proton or a lithium ion. The electrolyte layer In an electrochromic device, a may be a liquid electrolyte solution like lithium physical/chemical change is produced in response 70 perchlorate in propylene carbonate or a gel elec- to an induced electric field. The result is a change trolyte like polyvinyl butyral methanol doped with in the reflective (or transmissive) properties of the LiCI. The electrolyte layer may also be a solid device with respect to electromagnetic radiations, electrolyte which comprises polymers or e.g., UV, visible and IR radiations. Such devices, copolymers containing acidic groups such as poly- one embodiment being shown as item 10 in Figure 75 styrene sulfonic acid, propylene oxide or polyethyl- 1, generally comprise a film'of electrochromic ma- ene oxide. terial 12 and an ion conductive insulating layer 14 It would be desirable, however, to have an which functions as an electrolyte layer. The film electrochromic device which comprises less layers and the electrolyte layer are in surface contact with and is hence less complex to fabricate. Addition- each other for exchange of ions between the elec- 20 ally, it would be desirable if the device, in addition trochromic film and the electrolyte layer. Two con- to being able to reduce transmission of visible light, ductive electrode layers, 16 and 18 in Figure 1, at would also be able to substantially reduce trans- least one of them being transparent, are disposed mission of IR wavelength radiation, i.e., keep radi- on the opposite outer surfaces of the film and the ation of the type which generates heat from pass- electrolyte layer to provide means for applying a 25 ing through the device. This would be particularly voltage across the combined thickness of the elec- useful if the device is used as a window of a trochromic film and the electrolyte layer. As shown building or automobile. in Figure 1, electrode layers are provided on sub- The present invention is directed to an elec- strates 20 and 22, which substrates may be of a trochromic device comprising a substrate; a first material such as glass. Depending on the ion pro- 30 electrode member provided on the substrate; an viding and ion storage capacity of ion conductive electrochromic matrix material layer in contact with layer 16, a counter electrode located between ion the first electrode member; and a second electrode conductive layer 14 and electrode layer 18 may be member in contact with the electrochromic matrix used. The electrodes are provided with external material layer, at least one of the first and second electrical leads 24 and 26 connected to a voltage 35 electrode members being transparent, the elec- providing source 28. Application of a voltage of trochromic matrix material layer consisting essen- proper polarity across the electrodes causes color- tially of a substantially uniform mixture of: (i) a ation of the electrochromic layer. By reversing the metal salt component selected from the group con- polarity of the applied voltage, the colored elec- sisting essentially of halides, acetates, nitrates, sul- trochromic layer will be uncolored (bleached). 40 fates, and phosphates of metals selected from the Changing from the bleached state to the colored group consisting essentially of copper, cobalt, nick- state or from the colored state to the bleached el, lead, molybdenum, rubidium and tin; (ii) an ion state is termed "switching". The electrochromic conductive material component selected from a material may be "persistent" in its colored state group consisting essentially of solid electrolytes which means that it has the ability to remain, after 45 and gel electrolytes; and an ion conduction enhan- removal of the electric field, in the absorptive state cer component selected from the group consisting to which it is changed, as distinguished from a essentially of lithium salts and sodium salts. Prefer- substantially instantaneous reversion to the initial ably, the metal salt is present in the matrix layer in state. The length of time a material is persistent is an amount sufficient to provide a maximum thick- called its "open circuit memory" or simply 50 ness of between about 500 to 1000A of the metal "memory". Electrochromic devices of this type on an electrode member when a voltage is applied have been described for several uses, such as for across the electrodes. The device may further image display, for light filtering, etc. See, e.g., U.S. comprise a second substrate adjacent to the sec- Patent Nos. 3,708,220, 4,194,812; 4,278,329; ond electrode member. According to another as- 4,645,308; 4,436,769; 4,500,878; 4,150,879; pect of the invention, it is directed to the method of EP 0 392 694 A2 making the above device. layer; and a second electrode member. The elec- When a voltage is applied across the elec- trochromic matrix material layer (prior to application trodes of the device, the electrode member which of a voltage across the electrode members) con- functions as the cathode takes on a metallic ap- sists essentially of a substantially uniform mixture pearance which makes the device useful as a dis- 5 of (i) a metal salt component, (ii) an ion conductive play device. Additionally, embodiments of this de- enhancer component and (iii) an ion conductive vice are particularly useful as windows of buildings material component. The device may further com- or automobiles since they are capable of more prise a second substrate adjacent to the second effectively reflecting IR radiation than are conven- electrode member. tional electrochromic devices. Thus embodiments 70 One aspect of the invention will be further of the present invention device, if used as windows, understood by reference to Figure 2. This figure offer an enhanced ability over prior art electroch- depicts a cross sectional view of an embodiment of romic devices to keep heat out of the building or a device 30 according to the invention taken along automobile, while at the same time being capable a line perpendicular to a surface of a substrate of of keeping heat within the building or automobile 75 the device, before and after application of a voltage from escaping through the device. This is in addi- across the electrodes of the device. The device 30 tion to the ability of these devices to control the in Figure 2 comprises glass substrate 32 in contact amount of visible light which may enter the building with transparent electrode member 34 and glass or vehicle. Still further, it has been found that substrate 36 in contact with transparent electrode embodiments of the device of the present invention 20 member 38. The device further comprises a layer are able to be switched to the colored state by of electrochromic matrix material 40 according to means of a relatively low voltage applied across the present invention, shown before, "a", and after, the electrodes. "b", application of a voltage across the electrodes. The thickness of the metallic layer formed dur- The electrochromic matrix layer 40 (before applica- ing operation of the device and hence the cor- 25 tion of a voltage across the electrodes) consists responding reduction in transmission of radiation essentially of a substantially uniform mixture of by the device can be controlled by the length of components (i), (ii), and (iii) as described above. In time a voltage is applied across the electrodes of the particular embodiment shown in Figure 2, these the device. That is, the longer the voltage is ap- components are copper chloride, lithium nitrate and plied, the thicker the metallic layer formed with a 30 polyvinyl butyral gel, respectively.
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