Note: Descriptions are shown in the official language in which they were submitted.
1015202530CA 02265190 1999-03-10Le A 32 912âForeign Countries TS/ngb/NT-1-Process for producing an ion storage layer for electrochromic systemsThe present invention relates to a process for producing an inorganic ion storagelayer for electrochromic systems with controllable transparency for light.It has not been possible to date to regulate the transparency of vehicle windows toelectromagnetic radiation. To date, phototropic glasses have been used only asspectacle lenses, and feature only a relatively small change in transmission. Windowsin buildings have to date been darkened using curtains, shutters, rollers or othermovable mechanical elements.Electrochromic devices can, therefore, be employed in a wide variety of ways. Anoverview may be given by the following examples:1.Vehicle glazing (windows or car sunroofs)An electrochromic device is suitable for anti-sun or anti-dazzle use in motorvehicles. The front, side and rear windows or sunroofs can maybe included.The degree of darkening can be adapted continuously and in zones to theneeds of the driver, to the sunâs position and to the current driving situation.Integration into a computer-controlled control system is an option. A furtheroption is the combination of the active element with a laminated glass unit,such as the application of a ï¬lm system to the safety windows.The transparency of the windows can be controlled manually or auto-matically, a feature which can be utilized for effective antiâdazzle protectionwhen travelling at night, automatic adaptation of the level of lightness whenentering and emerging from tunnels and multiâstorey/underground car parks,and for protection against break-in and robbery from the parked vehicle, bypreventing sight of the vehicle interior. Excessive heating of the interior insummer, especially when the vehicle is parked, can be prevented.1015202530CA 02265190 1999-03-10Le A 32 912-Foreign Countries(cf. e.g. EP-A-0 272 428)Glazing in buildings (electrochromic window)In buildings, electrochromic systems are suitable for use for darkening thewindows and skylights of buildings, living areas, working areas or green-houses as a form of controllable protection from sunlight (visible spectralrange) and against heat (IR range) and as visible screening (visible spectralrange). To protect against break-ins, the glazing of counters in banks or ofshop windows can be darkened at the push of a button. Glass doors can bemade visible automatically when approached in order to avoid injuries. Thepossibility of producing virtually all shades of colour also permits the glazingto be incorporated as a design element into the facade of a building. Theenergy consumption for control of the transparency of large areas of windowis low, especially when the memory effect of the system can be utilized andenergy is consumed only in the switchover phase. Combination with a heatinsulation glazing (K glass) is highly suited for ensuring dynamic control ofsolar irradiation by a âsmartâ window. Consequently, an electrochromicsystem can contribute to regulating and limiting the energy required for airconditioning.The system can also be supplied with a voltage by means of solar modules. Aphotosensitive sensor can determine the degree of solar irradiation and thuscontrol the degree of light transmission accordingly.Display elementsThe possibility of attractively coloured design and the large-scale depiction ofany desired indicia, e.g. letters, numbers, signs and symbols (which can beproduced by means of suitable structuring techniques), provides a medium1015202530CA 02265190 1999-03-10Le A 32 912-Foreign Countrieswhich is of interest for advertising. Decorative and informative effects arereadily possible.In addition to the possibility of arranging the system between glass platesthere is also the alternative of using two or just one transparent plastics ï¬lmas a support. By this means it is possible to realise posterlike advertisingmedia with alterable information.Electrochromic devices can be used for small display elements such as facesof clocks or dials of measuring instruments, displays for a wide variety ofuses and for large display elements such as traffic signs, advertising columns,displays at railway stations and airports, or for guided parking systems. Theiruse as a variable line marking system (pitch boundaries, etc.) in sports halls isanother possibility.They can be used generally wherever information is to be made visible.OpticsIn optics the use of electrochromic systems is possible both in combinationwith glasses, lenses and filters of other optical devices and also as a stand-alone, actively utilized component. A further possibility is that of applicationas protection for optical detection systems against dazzle. The system islikewise suitable as a controllable ï¬lter system for photographic processes.MirrorsAn electrochromic device can also be employed as a dimmable mirror â forexample, for a car exterior or internal rearview mirror which can be darkenedby applying an electrical voltage, so preventing the driver from being dazzledby the headlights of other vehicles (cf. e.g. US-A-3,280,702, US-A-1015202530CA 0g26s190 1999-03-10Le A 32 912-Foreign Countries4,902,108, EPâA-0 435 689, US-A 5,140,455). Disadvantageous in prior artsystems (solution systems) is the lack of colour homogeneity followingprolonged operation (segregation), especially in the case of large-sizedmirrors (e. g. lorry mirrors). An increase in the viscosity of the solution systemby adding polymeric thickeners is described (e.g. US-A-4,902,108).6. EMI shieldingAn electrochromic device can also be used as a variable ï¬lter element for themodulation of electromagnetic radiation within certain wavelength ranges.Electrochromic devices normally consist of a pair of glass plates, one of them beingmirrored in the case of a mirror. One side of these plates is coated with a transparentelectrically conductive layer of, for example, indium-tinâoxide (ITO). A cell isconstructed from these plates by ï¬xing them with their electrically conductivelycoated sides facing one another, the cell between the plates comprising theelectrochromic system, which in certain cases includes an ion storage layer. The cellis tightly sealed. By way of the conductive layer, the two plates can be contactedelectrically, and controlled, separately.In the case of the electrochromic solution systems known from the prior art citedabove there are, present in a solvent, pairs of redox substances which followingreduction and oxidation, respectively, form coloured free radicals, cationic freeradicals or anionic free radicals which are chemically reacted. Examples of suchredox couples are the viologen systems, which have been known for a long time.As the pair of redox substances, or redox couples, in such cases use is made of onereducible and one oxidizable substance. Both are colourless or have only a weakcoloration. Under the inï¬uence of an electrical voltage, one substance is reduced andthe other oxidized, with at least one becoming colored in the process. After the1015202530_ CA 0g26s190 1999-03-10Le A 32 912-Foreign Countriesvoltage is switched off, the two original redox substances are formed once more,which is accompanied by the disappearance or fading of the colour.US-A-4,902,108 discloses that suitable such redox couples are those where thereducible substance has at least two chemically reversible reduction waves in thecyclic voltarmnogram and the oxidizible substance, correspondingly, has at least twochemically reversible oxidation waves. Systems of this kind are suitable primarily foranti-glare car rearview mirrors. Since these are solution systems, their use inelectrochromic windows does not come into consideration under normal circum-stances.Also known are systems where the actual electrochromic redox couple is dispersed ina polymer matrix (see e.g. WO-A-963475).Combinations of inorganic electrochromic components, such as W03 , NiO or IrO2,for example, are likewise known and are suitable as components in an electrochromicwindow (see e.g. USâA-5,657,149, Electronique International No. 276, 16 (1997);Saint-Gobain).These inorganic electrochromic components can be applied to the conductivesubstrate only by vapour deposition, sputtering or a solâgel technique. The result ofthis is that systems of this kind are very expensive to produce. In the effort to replacean inorganic component by an organic polymer component, electrochromic systemsbased on the electrically conductive polymer polyaniline (PANI) and W03 ascomplementary electrochromic materials, for example, have been disclosed (see e.g.B. P. Jelle, G. Hagen, J. Electrochem. Soc., Vol. 140, No. 12, 3560 (1993)). Theattempt has also been made to employ systems without an inorganic component, inwhich the ITO or SnO2 coat (counter-electrode) is intended to act as a complemen-tary electrochromic component to substituted poly(3,4-ethylenedioxythiophenes)(US-Aâ5,l87,608).1020CA 02265190 1999-03-10However, it is found that electrochromic systems ofthis kind are incapable of ensuring a sufficient number ofswitching cycles without altering the device properties, since,apparently, the ITO or SnO2 coat degrades after a number ofswitching cycles and/or the intercalation of Li ions added isnot reversible. For reversibility and hence ultimately forcycle stability there is a need for an ion storage layer, whichto date it has only been possible to produce by vapour deposi-tion, sputtering or a solâgel technique under drastic heattreatment conditions. The latter condition of preparation rulesout the use of plastics substrates.It is an object of the present invention to develop aproduction process for a suitable inorganic ion storage layer,which does not have the aboveâmentioned disadvantages of theproduction processes known to date. In particular, theproduction process should be sufficiently gentle that evenplastics substrates can be used in electrochromic systems.It has now been found that an inorganic ion storagelayer can be produced from vanadium oxide or niobium oxide, orfrom vanadium oxide or niobium oxide comprising lithium ions,by a very gentle solâgel process.According to one aspect of the present invention,there is provided process for producing an ion storage layerfrom vanadium oxide or niobium oxide, or from a vanadium oxideor niobium oxide comprising lithium ions, for an electrochromiclayer system, in which the ion storage layer is produced froman aqueous solution on a substrate by a solâgel process withina temperature range from 40 to 150°C.23189-837210CA 02265190 1999-03-10_ 6a -The present invention further provides a process forproducing an ion storage layer from vanadium oxide or from avanadium oxide comprising lithium ions for an electrochromiclayer system, where the ion storage layer is produced from anaqueous solution by a solâgel process within a temperature rangefrom 40 to 150°C.Preference is given to layers of inorganic ion storesbased on vanadium oxide or niobium oxide, of the formulae (I)to (VI):V205 (I)LixV2O5 (II)LixV2O5+X/2 (III)Nb2O5 (IV)23189-83721015202530CA 02265190 1999-03-10Le A 32 912-Foreign Countries_ 7 _LixNb2O5 (V)I-ixNb205+x/2 (V1)wherex represents numbers from 0.001 to 5, preferably from 0.001 to 3.The ion storage layers can be produced by a very gentle sol-gel process.The procedure is as follows:An aqueous solution of ammonium metavanadate (NH4VO3) or ammoniummetaniobate (NH4NbO3) is treated â by stirring, for example â with a cation ex-changer in order to replace the ammonium cation by protons. Following removal ofthe cation exchanger by ï¬ltration, the resulting solution is left to stand (ageing). Thetime for which the solution is required to rest depends on the ambient or solutiontemperature. At room temperature, for example, the solution should be left to standfor at least 3 hours. At higher temperatures even markedly shorter times aresufï¬cient, for example just 30 minutes.Subsequently, the solution is applied - for example, by pouring, spraying or the like -to the electrically conductive side of the substrate which is subsequently heat-treatedat temperatures of from 40 to 150°C, preferably from 40 to 130°C.In this way a layer of the ion store is obtained which has excellent reversibility inrespect of the lithium ion intercalation and decalation.The compounds of the formulae (1) to (V1) are commonly known compounds whichare obtainable commercially or can be prepared by commonly known methods ofinorgnaic chemistry (cf. e.g. Rompp Chemie Lexikon; Chem. Abstr. 1313-96-8;Hollemann-Wiberg, Lehrbuch der Anorganischen Chemie, 71st - 80th edition,Walter de Gruyter & Co., Berlin 1971, (e.g. pages 779-781)).1015202530CA 0g26s190 1999-03-10Le A 32 912-Foreign Countr1esTo improve wetting of the substrates with the aqueous solution it is also possible toadd a wetting agent (for example, a ï¬uorosurfactant).An Li salt can be added to the aged solution, or else the aged solution without thissalt can be applied to the substrate and then heat-treated, which can be carried outunder reduced pressure or at atmospheric pressure.Suitable and preferred Li salts are LiClO4, LiCF3SO3, LiN(SO2CF3)2, LiCl, LiPF6.Among these, very particular preference is given to LiClO4, LiCF3SO3 andLiN(SO2CF3)2.The compounds are widely known and obtainable commercially or can be preparedby widely known methods of inorganic chemistry.The production process of the invention for ion storage layers in electrochromicsystems can be applied to glass or different types of plastic as the substrate.Preference is given to transparent substrates of whatever kind which are providedwith an electrically conducting transparent coating or with a mirror layer.Particularly preferred materials other than glass, especially heat insulation glass inthe case of application as an electrochromic window (in layer thicknesses of 10 pmin the case of ï¬exible glass and thin glass up to 3 cm), are polyesters (e.g.polyethylene terephthalate) (PET), various types of polycarbonate (e.g. ®Makrolon,APEC-HT), and polycyclooleï¬ns. In this case the polymeric substrate can beemployed as a ï¬exible ï¬lm or as a thick plate. The substrate may also be in curvedform.In addition, the plastics substrates can be provided with barrier layers against waterand oxygen.1015202530CA 02265190 1999-03-10Le A 32 912-Foreign CountriesThe production process of the invention for the ion storage layers is one productionstep in the overall production of an electrochromic system. In an electrochromicsystem the production process of the invention serves as a substep in the generationof an electrochromic layer structure as a medium with variable transmission; in otherwords, under the inï¬uence of an electrical voltage the transparency of the systemalters as it passes from a colorless into a coloured state.The present invention additionally provides for the incorporation of the productionprocess of the invention into the production of an electrochromic device.Applications of this electrochromic device are, for example, as a window pane, carsunroof, car rearview mirror, display or optical element.Examples:Example 1Production of an ion storage layer 1 (V205)a) Preparation of a sol solution for producing the ion storage layer2.5 g of ammonium vanadate (NH4VO3) are dissolved in 25 g of water, and37.5 g of the ion exchanger Lewatit S100 (from Bayer AG, Leverkusen,Germany) are added. The mixture is subsequently stirred at room temperturefor ten minutes. Then, with rapid stirring, a further 475 g of water are addedand stirring is continued for 10 minutes. The mixture is filtered and theresulting solution is allowed to stand at room temperature for 24 hours, forageing. Finally, 0.25 g of the ï¬uorosurfactant wetting agent Fluortensid FT248 (from Bayer AG Leverkusen, Germany) is added. This solution is readyfor use.10152025CA 02265190 1999-03-10Le A 32 912-Foreign Countries-10-b) Gel prckzessThe solution from Example la) is applied to the conductive side of ITO glassand a uniform layer of the sol is produced using a spin coater (10 seconds at1000 rpm). This is followed by heat treatment at 60°C for 24 hours. A layerthickness measurement with the proï¬lometer gave a result of 10 to 20 nm.Example 2Production of an ion storage layer 2 (LixV2O5)0.01 g of LiCF3SO3 (Li triï¬ate from Aldrich) is added to 1 g of the solution fromExample la), and the mixture is stirred thoroughly. As described under lb), thissolution is applied to the conductive side of K glass (FTO) and in the course of twohours of heat treatment at 100°C an ion storage layer is formed which, however,unlike that of Example lb), already includes Li ions.Example 3Production of an ion storage layer 3 (V205)The solution from Example la) is applied to the conductive side of K glass and auniform layer of the sol is produced using a spin coater (10 seconds at 1000 rpm).This is followed by heat treatment at 100°C for 2 hours. A layer thicknessmeasurement with the proï¬lometer gave a result of 10 â 20 nm.CA 02265190 1999-03-10Le A 32 912-Foreign Countries-11-Example 4Construction of electrochromic cells for testing the ion storage layers:1015202530Application of an electrochromic polymer to an ITO substrate:Baytron®P (aqueous dispersion of the conductive polymer PEDT/PSSpolyethylenedioxythiophene-polystyrenesulfonate, from Bayer AG) is appliedfrom aqueous solution using a spin coater 4 times for 15 seconds each time ata speed of rotation of 1500 rpm to the electrically conductive side of an ITOglass sheet (from Merk-Balzers, Liechtenstein, surface resistance <15 Q/sq).During application, the solvent is evaporated using a hairdryer.A transparent and only very slightly bluish-coloured polymer ï¬lm is obtained.Measurement of the layer thickness with a proï¬lometer gave a value of0.6 pm.Application of Baytron P to K-Glass:Baytron®P is applied from aqueous solution using a spin coater 4 times for 15seconds each time at a speed of rotation of 1500 rpm to the electricallyconductive side of a K glass sheet (FTO, heat insulating sheet from Flachglas,surface resistance ~20 Q/sq). During application, the solvent is evaporatedusing a hairdryer.A transparent and only very slight bluish-coloured polymer ï¬lm is obtained.Measurement of the layer thickness gave a value of 0. 6 pm.Preparation of a gel electrolyte 1:The following mixture is produced:7.0 g of acetonitrile2.0 g of propylene carbonate (dry)0.7 g of PMMA (MW about 15.000)0.3 g of CF3SO3Li (from Aldrich)1015202530CA 02265190 1999-03-10Le A 32 912-Foreign Countries-12-After all of the components have dissolved, the solution is ï¬ltered once and isready for use.Preparation of a gel electrolyte 2:The procedure is analogous but with the following amounts of components:7.0 g of acetonitrile2.0 g of propylene carbonate0.7 g of polyethylene oxide (PEO; MW about 200,000)0.3 g of CF3SO3Li (from Aldrich)Production of a gel electrolyte layer 1:The gel electrolyte 1 is applied using the spin coater to the ion storage layer 1(30 seconds at 1000 rpm). In the course of application the highly volatileacetonitrile evaporates almost completely to leave the gel electrolyte as alayer.Production of a gel electrolyte layer 2:The gel electrolyte 2 is applied using the spin coater to the ion storage layer 1(30 seconds at 1000 rpm). In the course of application the highly volatileacetonitrile evaporates almost completely to leave the gel electrolyte as alayer.Production of a gel electrolyte layer 3:The gel electrolyte 2 is applied using the spin coater to the ion storage layer 2(30 seconds at 1000 rpm). In the course of application the highly volatileacetonitrile evaporates almost completely to leave the gel electrolyte as alayer.Production of a gel electrolyte layer 4:The gel electrolyte 2 is applied using the spin coater to the ion storage layer 3(30 seconds at 1000 rpm). In the course of application the highly volatile10152025CA 02265190 1999-03-10Le A 32 912-Foreign Countries-13-acetonitrile evaporates almost completely to leave the gel electrolyte as alayer.0 Finishing of a complete electrochromic cell 1 and 2:Gel electrolytes 1 and 2 are applied uniformly to the ion storage layer 1 onITO glasses and the coated glasses are brought into contact with the BaytronPâcoated sides of ITO glass substrates. This gives electrochromic layersystems which are characterized in Example 5.0 Finishing of a complete electrochromic cell 3 and 4:Gel electrolytes 2 are applied uniformly to the ion storage layer 2 and 3 on Kglasses and the coated glasses are brought into contact with the Baytron P-coated sides of K glass substrates. This gives electrochromic layer systemswhich are characterized in Examples 6 and 7.Example 5Cycle stability test on the electrochromic cells 1 and 2The electrochromic cells 1 (with PMMA) and 2 (with PEO) from Example 4 are eachcontacted at the conductive layers of the coated ITO glasses with 1.6 V DC voltagefor a short time before the polarity of the electrical stimulus is changed. Thisproduces a cyclical colouring and decolouring of the cell. At the same time thechange over time in the transmission of the cell is observed. It is found that systemswith the ion storage layers produced in accordance with the invention exhibit stableswitching behaviour (in this respect compare Fig. 1).101520CA 02265190 1999-03-10Le A 32 912-Foreign Countries-14-Example 6Cycle stability test on the electrochromic cell 3The electrochromic cell 3 (with PEO on LixV2O5) from Example 4 is in each casecontacted at the conductive layers of the coated K glasses with 1.5 V DC voltage fora short time before the polarity of the electrical stimulus is changed. This produces acyclical colouring and decolouring of the cell. At the same time the change over timein the transmission of the cell and the current through the system are observed. It isfound that systems with the ion storage layer produced in accordance with theinvention exhibit stable switching behaviour (in this respect compare Fig. 2).Example 7Cyclovoltametric investigation of the electrochromic cells 3 and 4The electrochromic cells 3 (with PEO on LiXV2O5) and 4 (with PEO on V205) fromExample 4 are characterized by cyclovoltametry in a two-electrode setup withoutreference between +2 V and -2 V (pole reversal) with respect to their currentâvoltagecharacteristic lines. As can be seen in Fig. 3, the electrochemical proï¬le of propertiesand hence the switching behaviour of the system can be varied by way of the choiceof production conditions of the ion storage layers.
