WO2008150851A1

WO2008150851A1 - Monolithic architecture and electrolyte for electrochromic devices

Info

Publication number: WO2008150851A1
Application number: PCT/US2008/065062
Authority: WO
Inventors: Nigel Leyland; David Corr; Micheal Cassidy; Francois Pichot; Nikolaos Vlachopoulos; Michael Ryan
Original assignee: Ntera, Inc.
Priority date: 2007-06-01
Filing date: 2008-05-29
Publication date: 2008-12-11

Abstract

In a preferred embodiment, each segment of an electrochromic display Is formed In a monolithic stack on a substrate A control element is disposed on the substrate, followed by an insulating layer, a common electrode layer, a reflector layer, and a segment layer having an adsorbed electrochromophore Vertical conductors electrically couple the control element to the two electrodes An electrolyte, which may be a solid or liquid, permeates the monolithic stack and is contained by a frontplane In addition, the electrolyte may be isotropically or anisotropically conductive Vertical insulators separate neighboring segments In an alternative embodiment, the control element is placed on an opposing side of the substrate and is electrically coupled to the monolithic stack by way of a via hole The present invention improves electrochromic display performance by reducing the length of drive elements, and by reducing ionic crosstalk between neighboring segments

Description

[0001] MONOLITHIC ARCHITECTURE AND ELECTROLYTE FOR

ELECTROCHROMIC DEVICES

[0002] FIELD OF INVENTION

[0003] The present invention generally relates to electrochromic devices.

More particularly, the present invention relates to a monolithic architecture for an electrochromic device and electrolytes used with the device.

[0004] BACKGROUND

[0005] Electrochromic compounds exhibit a reversible color change when the compounds gain or lose electrons. Electrochromic devices that exploit the inherent properties of electrochromic compounds find application in large area static displays and automatically dimming mirrors, and are well known. Electrochromic display devices create images by selectively modulating light that passes through a controlled region containing an electrochromic compound. A multitude of controlled electrochromic regions may individually function as pixels to collectively create a high resolution image. Typically, these display devices contain a reflective layer underneath the electrochromic compound, respective to the viewer, for reflecting light allowed to pass beyond the electrochromic region. Simply put, the electrochromic pixel acts as a shutter either blocking light or allowing light to pass through to the underlying reflective layer. [0006] A typical prior art electrochromic display device, as shown in Figure

1, includes a base substrate 10, typically glass or plastic, which supports a transparent conductor layer 20, which may be, for example, a layer of fluorine doped tin oxide (FTO) or indium doped tin oxide (ITO). A nanoporous- nanocrystalline semi-conducting film 30, (herein referred to simply as a nano- structured film 30), is deposited, preferably by way of screen printing with an organic binder, on the transparent conductor 20. The nano-structured film is typically a doped metal oxide, such as antimony tin oxide (ATO). Optionally, a redox reaction promoter compound is adsorbed on the nano-structured film 30. An ion-permeable reflective layer 40, typically white titanium dioxide (Tiθ2), is optionally deposited, preferably by way of screen printing with an organic binder followed by sintering, on the nano-structured film 30.

[0007] A second substrate 50, which is transparent, supports a transparent conductor layer 60, which may be a layer of FTO or ITO. A nano-structured film 70 having a redox chromophore 75, typically a 4,4'-bipyridinium derivative compound, adsorbed thereto is deposited on the transparent conductor 60, by way of a self-assembled mono-layer deposition from solution.

[0008] The base substrate 10 and the second substrate 50 are then assembled with an electrolyte 80 placed between the ion-permeable reflective layer 40 and the nano-structured film 70 having an adsorbed redox chromophore 75. A potential applied across the cathode electrode 90 and the anode electrode 100 reduces the adsorbed redox chromophore 75, thereby producing a color change. Reversing the polarity of the potential reverses the color change. When the redox chromophore 75 is generally black or very deep purple in a reduced state, a viewer 110 perceives a generally black or very deep purple color. When the redox chromophore 75 is in an oxidized state and generally clear, a viewer 110 will perceive light reflected off of the ion-permeable reflective layer 40, which is generally white. In this manner, a black and white display is realized by a viewer 110.

[0009] Electrochromic display devices such as the one described above are described in greater detail in U.S. Patent No. 6,301,038 and U.S. Patent No. 6,870,657, both to Fitzmaurice et al., which are herein incorporated by reference. [0010] Large electrochromic pixels are difficult to switch for a variety of reasons. Large pixels are generally pixels larger than several hundred micrometers in at least one dimension. Because of the nature of electrochromic components, the switching time in a large pixel may be too long to result in an aesthetically pleasing visual change. In addition, the electrochromic compound contained in each pixel may not be completely switched, that is the pixel may not appear completely colored or completely clear, after the pixel settles. [0011] These disadvantages in prior art electrochromic devices are attributable to at least the following two effects. First, the conductive or semiconductive material used in the devices generally does not have a satisfactory conductance to support efficient and aesthetically desirable pixel switching. In other words, the conductive or semiconductive material cannot provide the necessary charge flux to the electrochromic compound. Second, the routing tracks on displays with large pixels are too long to allow quick conduction of the switching signals. The routing tracks in prior art displays originate on the periphery of the display and are therefore relatively long, particularly for pixels located in the middle of the display.

[0012] Accordingly, an electrochromic display architecture that allows rapid and efficient coloring of relatively large electrochromic pixels is desired.

[0013] SUMMARY

[0014] The present invention is a monolithic architecture for an electrochromic device. In a preferred embodiment, each segment of an electrochromic display is formed in a monolithic stack on a substrate. A control element is disposed on the substrate, followed by an insulating layer, a common electrode layer, a reflector layer, and a segment layer having an adsorbed electrochromophore. Vertical conductors electrically couple the control element to the segment electrode and the common electrode. An electrolyte permeates the monolithic stack. If desired, a frontplane can be included to exclude effects from the external environment or contain a liquid electrolyte. If the contents of the device do not need to be protected from the environment, or the electrolyte is otherwise contained a frontplane is not required. Vertical insulators separate neighboring segments. In an alternative embodiment, the control element is placed on an opposing side of the substrate and is electrically coupled to the monolithic stack by way of a via hole. The present invention improves electrochromic display performance by reducing the length of drive elements, and by reducing ionic crosstalk between neighboring segments.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A more detailed understanding of the invention may be had from the following description, given by way of example and to be understood in conjunction with the accompanying drawings, wherein:

[0017] Figure 1 is a direct-drive prior art electrochromic display device; and

[0018] Figure 2 is a monolithic architecture for an electrochromic device in accordance with the present invention.

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0020] Referring to Figure 2, an electrochromic display device architecture in accordance with the present invention includes monolithic segments 200 and an electrolyte 210. The electrolyte may be a solid or liquid electrolyte and in either case the electrolyte permeates the segments 200 The electrolyte may also form a seal, excluding the atmosphere from the segment. A backplane substrate 220 supports the monolithic segments 200. In a preferred embodiment, the backplane substrate is a printed circuit board (PCB). Alternatively, the backplane substrate is any suitable substrate capable of supporting the electrochromic device. For example, glass, Schott glass, plastic, and other rigid and flexible materials are suitable backplane substrates 220. [0021] Each monolithic segment comprises a control element 225, a non- permeable dielectric layer 230, an optional indium tin oxide (ITO) layer 235, a first mesoporous antimony tin oxide (ATO) layer 240, a mesoporous reflector layer 245, a second mesoporous ATO layer 250, which may alternatively be comprised of mesoporous ITO, and finally a nanostructured titanium dioxide layer 255 having an adsorbed electrochromophore. The second mesoporous ATO layer 250 and the nanostructured titanium dioxide layer 255 are preferably transparent, such that when the nanostructured titanium dioxide layer 255 is not electrically charged, a viewer 280 perceives light reflected from the mesoporous reflector layer 245.

[0022] An optional frontplane 260 is disposed above the segments 200 and in the case where the electrolyte 210 is a liquid, contains the electrolyte 210 inside the device. The frontplane 260 may be any transparent material, such as glass or plastic, and may be rigid or flexible. A seal (not shown) may be provided between the backplane substrate 220 and the frontplane 260. The seal may be an ultraviolet curable polymer. The frontplane 260 may be useful to exclude environmental substances. For example, if the electrochromophore or any other component is sensitive to oxygen, the frontplane may reduce oxygen contact with the interior of the device.

[0023] The control element 225 controls the electrical potential applied to each respective monolithic segment. Preferably, the control element is a thin film transistor (TFT). In this manner, an active matrix of monolithic segments 200 may be realized. Preferably, the control element 225 is an n-channel metal- oxide-semiconductor field-effect (NMOS) TFTs. Alternatively, the control elements 225 may be p-channel metal-oxide-semiconductor field effect (PMOS) TFTs, complementary-symmetry metal-oxide-semiconductor field effect (CMOS) TFTs, thin film diodes (TFDs), micro-electromechanical structures (MEMS), or any other type of active device capable of being matrix addressed for switching the monolithic segments 200.

[0024] The non-permeable dielectric layer 230 is preferably a spin-coated polymer, such as polyimide. The non-permeable dielectric layer 230 is non- permeable to the electrolyte 210. This protects the control element 225 from the corrosive effects of the electrolyte 210. The non-permeable dielectric layer 230 may be a single, monolithic layer, or it may comprise multiple layers of identical or different materials having desired properties to achieve a desired three dimensional structure. In a preferred embodiment, the non-permeable dielectric layer 230 is reflective. The reflective property of the non-permeable dielectric layer 230 may be inherent in the material that comprises the layer, or reflective particles may be interspersed in the non-permeable dielectric layer 230. As illustrated, vertical non-permeable dielectric layers 231 may also be included. [0025] The optional ITO layer 235 may be provided in order to increase the conductivity of the first mesoporous ATO layer 240. Preferably, the conductivity of the ITO layer 235 is greater than the conductivity of the first mesoporous antimony tin oxide (ATO) layer 240, which serves as the common electrode of the electrochromic segment. The optional ITO layer 235 enhances the switching properties of the monolithic segment 200 by improving charge transfer. It is noted that this optional ITO layer 235 is mesoporous, thereby facilitating charge transfer with the electrolyte 210 which permeates the mesoporous structure. [0026] The first mesoporous antimony tin oxide (ATO) layer 240, as noted above, is the common electrode of a monolithic segment 200. ATO is the preferred material for this layer 240 because of its capacity to accept charge. However, this property has the effect of slowing the switching speed of the monolithic segment 200. The aforementioned optional ITO layer 235 may be used to improve the switching speed while maintaining the inherent advantage of the ATO material. It is noted that this layer 240 is mesoporous, thereby allowing the permeation of the charge carrying electrolyte 210 throughout the layer 240. [0027] The mesoporous reflector 245 is preferably white in color. Most preferably, the mesoporous reflector 245 is rutile titanium dioxide. Again, it is noted that the mesoporous structure permits the permeation of charge carrying electrolyte 210 to lower layers.

[0028] The optional mesoporous ITO layer 250 serves a similar purpose for the nanostructured titanium dioxide layer 255 as the mesoporous ITO layer 235 serves for first mesoporous ATO layer 240. That is, the optional mesoporous ITO layer 250 enhances charge transfer and speeds switching of the monolithic segment 200. If the conductivity of the nanostructured titanium dioxide layer 255 is satisfactory, the optional mesoporous ITO layer 250 may be omitted as desired. Various design and operating criteria will determine whether the optional mesoporous ITO layer is required. It is noted that the mesoporous ITO layer 250 is permeable to the electrolyte 210, thereby allowing charge transfer through the layer 250.

[0029] The nanostructured titanium dioxide layer 255 preferably comprises a nano-structured titanium dioxide film. However, various metallic oxide semiconducting or conducting films may be used. The semiconducting or conducting metallic oxide may be an oxide of any suitable metal, such as, for example, titanium, zirconium, hafnium, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, silver, zinc, strontium, iron (Fe²⁺ or Fe³⁺) or nickel or a perovskite thereof or a conducting metallic oxide such as, for example, Indium Tin oxide (ITO), Antimony doped Tin Oxide (ATO), Fluorine doped Tin Oxide (FTO), Phosphorus doped Tin Oxide (PTO), or Aluminium doped Zinc Oxide (AZO). TK>2, WO3, Moθ3, ZnO, and Snθ2 are particularly preferred. Most preferably, the nano-structured film is titanium dioxide (Tiθ2) as mentioned above, and an adsorbed electrochromophore is adsorbed to the surface of the titanium dioxide film. Preferably, the electrochromophore is a compound of the general formulas I-III:

2X-

[0030]

[0031] 4X- I

III

[0033] R₁ is selected from any of the following: 0

(HO)₂P (CH₂)M HO(CH₂)M HOOC(CH₂)M (HO)₂B(CH₂)n

R2 is selected from C_1-10 alkyl, N-oxide, dimethylamino, acetonitrile, benzyl, phenyl, benzyl mono- or di-substituted by nitro; phenyl mono- or di-substituted by nitro. R3 is Ci_-10 alkyl and R4, R5, RΘ, and R7 are each independently selected from hydrogen, Ci-io alkyl, C₁No alkylene, aryl or substituted aryl, halogen, nitro, and an alcohol group. X is a charge balancing ion, and n = 1-10. [0034] Compounds of the formulae I-III are well known and may be prepared as described in Solar Energy Materials and Solar Cells, 57, (1999), 107- 125 which is hereby incorporated by reference in its entirety. In a preferred embodiment, the adsorbed electrochromophore is bis-(2-phosphonoethyl)-4,4'- bipyridinium dichloride.

[0035] It is noted that the nanostructured titanium dioxide 255 is mesoporous and permeable by the electrolyte 210.

[0036] A first vertical conductor 265 electrically couples the control element and the segment electrode, that is the nanostructured titanium dioxide layer 255, and optionally the optional ITO layer 250. Preferably, the first vertical conductor is resistant to possible corrosive effects of the electrolyte 210, and is most preferably made from nickel, a nickel alloy, or nickel plated. The various layers of the monolithic segment 200 may be formed to allow space for the vertical conductor 265, or the layers may be formed then etched to make way for the vertical conductor 265.

[0037] A second vertical conductor 266 electrically couples the control element and the common electrode, that is the optional indium tin oxide (ITO) layer 235 and the first mesoporous antimony tin oxide (ATO) layer 240. Preferably, the second vertical conductor is resistant to the corrosive effects of the electrolyte 210, and is most preferably made from nickel, a nickel alloy, or nickel plated. The various layers of the monolithic segment 200 may be formed to allow space for the second vertical conductor 266, or the layers may be formed then etched to make way for the vertical conductor 266.

[0038] In a preferred embodiment, a vertical insulator 270 may be placed between monolithic segments 200. The vertical insulator 270 isolates each monolithic segment 200 and prevents ionic crosstalk. This improves performance of the display and prevents coloration of neighboring segments. In one embodiment, the vertical insulator 270 extends to the frontplane 260, thereby isolating the electrolyte of each monolithic segment 200. In the embodiment illustrated in Figure 2, vertical insulator 270 and a vertical non-permeable dielectric layer 231 separate the segments. The vertical insulator may, however, extend to the substrate 220 and thereby supplement or replace the dielectric layer 231. Also, vertical insulator 270 may extend from frontplane 260 to substrate 220. The vertical insulator 270 may further support the frontplane and maintain a consistent spacing and thickness of the device. This embodiment is particularly advantageous for a flexible device, wherein both the substrate 220 and the frontplane 260 are flexible materials.

[0039] The various layers of the monolithic segment 200 may be deposited by way of a screen printing technique with an organic binder, optionally followed by a sintering step that removes the binder. Alternatively, each layer may be deposited by way of an inkjet printer. Binders may be chosen from compounds including, for example, ethyl cellulose, hydroxypropyl cellulose, poly (ethylene oxide), poly (methyl methacrylate), poly (vinyldiene fluoride), or alkyd resins including unsaturated carboxylic acids and glycerides thereof. [0040] In an alternative embodiment, the backplane substrate 210 is a printed circuit board (PCB). The control element 225 is placed on one side of the PCB while the monolithic segment 200 is placed on the opposite side of the PCB. A via hole is formed in the PCB and a conductor electrically couples the control element 225 to the monolithic segment 200. It is noted that the structure of the monolithic segment 200 remains the same as described above with reference to Figure 2. Specifically, it is noted that the layer containing the electrochromic material (i.e. the nanostructured titanium dioxide layer 255) is the uppermost layer with respect to a viewer 280 of the device. Moreover, when the electrolyte 210 is in excess of that needed to permeate a segment, it is generally above the monolithic segments 200. Electrolyte also permeates the various layers of each segment 200. Finally, it is noted that the segment electrode (i.e. the nanostructured titanium dioxide layer 255 and the optional ITO layer 250) are not formed on the frontplane 260, but are formed as the uppermost layer of the monolithic segment 200. [0041] The various embodiments described herein are well suited for large area semi-static displays, such as tileable signage. Additionally, the monolithic architecture described herein may be utilized in conjunction with an active or passive matrix. In the case of an active matrix driving scheme, the control elements 225 are controlled by way of an active matrix of electrodes. In the case of a passive matrix display, the vertical insulator 270 (or insulator 270 and layer 231 in combination) isolates each individual monolithic segment 200 thereby allowing passive addressing of individual segments.

[0042] While specific doped metal oxides, such as ATO and ITO, have been disclosed above, these materials may be interchanged and substituted with a wide variety of doped metal oxides depending on application. For example, fluorine tin oxide (FTO) may be used interchangeably with the above mentioned doped metal oxides. For the first mesoporous layer 240, any electrically conducting material that is chemically inert or passive in the electrolyte and may be formed into an ion-permeable mesoporous layer can be used, including, for example carbon, nickel, gold or platinum.

[0043] The electrolyte may comprise an ionic solid in liquid solution, an ionic liquid, an ionic solid in solid solution, an ionic liquid constrained within the pores of a solid polymer film or an ionic solid in liquid solution that is constrained within the pores of a solid polymer film. The electrolyte may additionally serve the function of forming a seal to exclude the atmosphere from the device. [0044] In an embodiment, the polymer film is prepared by precipitation. To prepare a film by precipitation, the polymer is dissolved in a carrier solvent. A wet film of the solution is then deposited onto the monolithic segment and allowed to percolate into the porous layers of the segment. The segment is then immersed in a second solvent. The polymer is insoluble in the second solvent, but the carrier solvent is miscible in the second solvent. As the two solvents mix, a phase inversion takes place in which the polymer solution, containing discrete polymer molecules in a continuous solvent phase; is replaced by a continuous polymer film. The mixed solvents are dispersed in discrete pores. The segment including the polymer film can then be removed from the solvent bath, dried, and the carrier and second solvents (working solvents) replaced with an electrolyte by soaking the segment including the film in the electrolyte. [0045] In an embodiment, polymers include, but are not restricted to poly

(vinylidene fluoride) (PVT)F), copolymers of vinylidene fluoride and hexafluoropropylene, poly (ethylene oxide), poly (vinyl alcohol), ethylcellulose, hydroxypropylcellulose, nitrocellulose, and poly (methylmethacrylate). Suitable solvents for the polymer include, but are not restricted to N-methylpyrrolidinone, acetone, gamma-butyrolactone, methoxypropionitrile, dimethylformamide, dimethylacetamide, alcohols, and glycol ethers or solutions of ionic compounds in these solvents, and mixtures thereof. Finally, suitable solvents for the electrolyte include, but are not restricted to gamma-butyrolactone, and methoxypropionitrile, and mixtures thereof.

[0046] In a preferred embodiment, where PVDF is the polymer the preferred carrier solvent is dimethylformamide, and the preferred second solvent is water. An alternate preferred carrier solvent is N-methyl pyrrolidinone and the alternate preferred second solvent is water.

[0047] In another embodiment, the film is prepared by solidification. To prepare a film by solidification, a melt is prepared by melting a mixture of two polymers or a polymer and a non-polymeric organic compound that are mutually soluble in the liquid phase and mutually insoluble or only sparingly soluble in the solid state. In a preferred embodiment, materials that form a eutectic system are chosen to form a polymer film by solidification.

[0048] Two-phase solids may form in a wide range of morphologies, depending on the crystal structures of the two solid components, their interfacial energy, the presence of suitable nucleation sites in the melt or its containing vessel, and the thermal profile of the material during solidification. In an embodiment, components used to make a polymer film by solidification are chosen in which the solid state consists of a continuous phase in a porous matrix in which the second phase may be continuous or discontinuous. [0049] In an embodiment, the material is cooled below the solidus temperature, and the non-continuous phase is removed by chemical dissolution. An electrolyte, consisting of an ionic material in liquid solution or an ionic liquid is introduced into the material by soaking or infiltration. [0050] In another embodiment, the components are chosen such that the first phase to solidify is the continuous one. The material is then maintained at a temperature above the liquidus, but below the solidus for that composition, so that the material remains in the two-phase region of the phase diagram. The discontinuous liquid is then removed by washing with a solvent with which it is miscible, but in which the continuous phase is insoluble. The electrolyte, consisting of an ionic material in liquid solution, or an ionic liquid, is introduced into the material by soaking or infiltration, as above.

[0051] In yet another embodiment, the components are chosen such that the first phase to solidify is the continuous one and the second component is an ionic material in liquid solution, or an ionic liquid. The second component is chosen to have a freezing point below the lower of the minimum operational or storage temperature of the device in which the electrolyte is to be used, thus maintaining the entire electrolyte system above the solidus temperature and in the two-phase region of the phase diagram. The second, liquid phase forms the electrolyte in the porous solid film. In this embodiment, the melt may be introduced into the display device and part-frozen, as above, in situ. In this case, the surfaces of the display electrodes may be used to provide nucleation sites for the growth of the solid phase, promoting columnar orientation of the structure, aligned perpendicular to the electrode planes.

[0052] In a further embodiment, the electrolyte is introduced in the form of a mixture comprising a liquid resin, a liquid compound that forms a solid copolymer with the resin in the presence of a chemical initiator, an ionic compound that is soluble both in the mixture of the first two components and in their copolymer, and an initiator for the formation of the copolymer. The mixture of the above components is prepared and introduced to the device before the polymerisation is complete and while the mixture is still liquid. The device assembly is completed while the mixture is still liquid and the polymerisation reaction is allowed to proceed to form a solid electroyte solution. [0053] In a further embodiment, the electrolyte is introduced in the form of a mixture comprising a liquid resin, a liquid compound that forms a solid copolymer with the resin when exposed to thermal radiation, an ionic compound that is soluble both in the mixture of the first two components and in their copolymer. The mixture of the above components is prepared and introduced to the device before the polymerisation is complete and while the mixture is still liquid. The device assembly is completed while the mixture is still liquid and the device is then heated to initiate and complete the polymerisation reaction, to form a solid electrolyte solution.

[0054] In a further embodiment, the electrolyte is introduced in the form of a mixture comprising a liquid resin, a liquid compound that forms a solid copolymer with the resin when exposed to ultraviolet or visible light, an ionic compound that is soluble both in the mixture of the first two components and in their copolymer. The mixture of the above components is prepared and introduced to the device before the polymerisation is complete and while the mixture is still liquid. The device assembly is completed while the mixture is still liquid and the device is then exposed to light to initiate and complete the polymerisation reaction, to form a solid electrolyte solution. [0055] Preferable monomers include, but are not restricted to methylmethacrylate, tert-butyl methacrylate, p-tert-butoxystryrene, acrylonitrile, ethylene oxide and vinylacetate. Preferable ionic liquids include, but are not limited to Ethanolammonium formate, l-Ethyl-3-methyl-imidazolium dicyanamide, l-Ethyl-3-methyl-imidazolium methanesulfonate, l-Ethyl-3- methyl-imidazolium nitrate, l-Ethyl-3-methyl-imidazolium tetrafluoroborate, 1- Ethyl-3-methyl-imidazolium ethylsulfate, l-Butyl-3-methyl-imidazolium bromide, Ethylammonium nitrate, Trihexyltetradecylphosphonium decanoate, and Triisobutylmethylphosphonium tosylate. Further ionic liquids suitable for these embodiments include Butylmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide, l-Ethyl-3-methylimidazolium chloride, 1- Ethyl-3-methylimidazolium trifuoromethanesulfonate, l-Butyl-3- methylimidazolium trifluoromethanesulfonate, l-Ethyl-3-methylimidazolium chloride, l-Ethyl-3-methylimidazolium chloride, l-Ethyl-3-methylimidazolium bromide, l-Butyl-3-methylimidazoliurα chloride, l-Butyl-3-methylimidazolium bromide, l-Hexyl-3-methylimidazolium chloride, l-Hexyl-3-methylimidazolium bromide, l-Methyl-3-octylimidazolium chloride, l-Methyl-3-octylimidazolium bromide, l-Propyl-3-methyliirridazolium iodide, l-Butyl-2,3-dimethyUmidazolium chloride, l-Ethyl-3-methylimidazolium tetrafluoroborate, l-Ethyl-3- methylimidazolium hexafluorophospate, l-Ethyl-3-methylimidazolium dicyanamide, l-Ethyl-3-methylimidazolium trifuoromethanesulfonate, l-Ethyl-3- methylimidazolium methanesulfonate, l-Butyl-3-methylimidazolium tetrafluoroborate, l-Butyl-3-methylimidazolium hexafluorophosphate, l-Butyl-3- methylimidazolium hexafluorophosphate, l-Butyl-3-methylimidazolium trifluoromethanesulfonate, l-Butyl-3-methylimidazolium methanesulfonate, 1- Hexyl-3-methylimidazolium tetrafluoroborate, l-Hexyl-3-methylimidazolium hexafluorophosphate, l-Methyl-3-octylimidazohum tetrafluoroborate, l-Methyl-3- octylimidazolium hexafluorophosphate, l-Butyl-2,3-dimethylimidazolium tetrafluoroborate, l-Butyl-2,3-dimethylimidazolium hexafluorophosphate, Cyclohexyltrimethylammonium bis(trifluormethylsulfonyl)imide, bis(trifluoromethylsulfonyl)imide, ECOENG™ 418, (2-

Hydroxyethyl)trimethylammonium dimethylphosphate, l-Ethyl-3- methylimidazolium tosylate, ECOENG™ 41M, ECOENG™ 2 IM, l-Butyl-4- methylpyridinium bromide, l-Butyl-3-methylpyridinium bromide, l-Butyl-3- methylpyridinium tetrafluoroborate, l-Butyl-4-methylpyridinium tetrafluoroborate, l-Butyl-4-methylpyridinium hexafluorophosphate, l-Butyl-3- methylpyridinium hexafluorophosphate, l-Ethyl-3-hydroxymethylpyridinium ethylsulfate, l-Ethyl-3-methylpyridinium ethylsulfate, l-Ethyl-3- methylpyridinium nonaflate, l-Butyl-3-methylpyridinium dicyanamide, 1-Metyl- 3-octylpyridinium tetrafluoroborate, Triethylsulfonium bis(triflouromethylsulfonyl)imide, Butylmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide, ECOENG™ 411, ECOENG™ 212, and ECOENG™. Preferable ionic solids include, but are not restricted to lithium perchlorate, lithium chloride, sodium chloride, lithium nitrate, sodium nitrate, lithium bromide, sodium bromide, potassium chloride, potassium bromide, lithium bistrifluorosulfonimide, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, tetramethylammonium tetrafluoroborate and lithium hexafluorophosphate.

[0056] Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention.

Claims

CLAIMS What is claimed is:

1. An electrochromic display device comprising: a frontplane, at least one segment, at least one control element, a substrate, and an electrolyte; the at least one segment comprising: a first layer located beneath the frontplane and including a nanostructured metal oxide film with an adsorbed redox chromophore, the redox chromophore including a first redox state and a second redox state, in the first state the redox chromophore absorbs more light than in the second state; a second layer located beneath the first layer and including a porous ion permeable electrically insulating material; a third layer located beneath the second layer and including an ion porous electrically conducting material; and a fourth layer located beneath the third layer and including an insulating material; the at least one control element operatively connected to the first and third layers; the substrate disposed below the segment; and the electrolyte permeating at least the first, second, and third layers, and contained between the frontplane and the substrate.

2. The electrochromic display device of claim 1, wherein the control element is disposed between the control element and the segment.

3. An electrochromic display device according to either claim 1 or 2, wherein the first layer has a conductivity lower than a predetermined threshold and a first additional layer is interposed between the first and second layer that includes a mesoporous electrically conducting ion permeable material.

4. An electrochromic display device according to any of the preceding claims, wherein the second layer is reflective.

5. An electrochromic display device according to any of the preceding claims, wherein the first layer is reflective when the redox chromophore is in the second redox state.

6. An electrochromic display device according to any of the preceding claims, wherein the substrate is a printed circuit board (PCB).

7. An electrochromic display device according to any of the preceding claims, further comprising a first via hole extending between the at least one control element and the first layer; and a first vertical conductor disposed in the via hole that electrically connects the control element to the first layer.

8. The electrochromic display device of claim 7, wherein the first vertical conductor is nickel plated.

9. The electrochromic display device of claim 7, further comprising a second via hole extending between the at least one control element and the third layer; and a second vertical conductor disposed in the second via hole that electrically connects the control element and the third layer.

10. The electrochromic display device of claim 9, wherein the second vertical conductor is nickel plated.

11. An electrochromic display device according to any of the preceding claims, wherein the conductivity of the third layer is less than a predetermined amount and a second additional layer is disposed beneath the third layer and includes an electrically conductive material.

12. An electrochromic display device according to any of the preceding claims, wherein the at least one control element is connected to a direct drive.

13. An electrochromic display device according to any of the preceding claims, wherein the substrate is a printed circuit board (PCB).

14. The electrochromic display device of claim 13, wherein the at least one control element is located beneath the printed circuit board and the operable connection to the first and third layers is made through via holes in the printed circuit board.

15. An electrochromic display device according to any of the preceding claims , wherein the at least one control element is an active element.

16. The electrochromic display device of claim 16, wherein the active element is disposed between the segment and the substrate.

17. An electrochromic display device according to either claim 15 or 16, wherein the active element is a thin film transistor (TFT).

18. An electrochromic display device according to any of claims 15-17, wherein the at least one control element includes a plurality of control elements connected in a matrix.

19. An electrochromic display device according to 15-17, wherein the at least one control element includes a plurality of control elements connected in a passive matrix.

20. An electrochromic display device according to any of the preceding claims further comprising a plurality of segments and vertical insulators extending from the substrate to the frontplane and isolating each of the plurality of segments.

21. An electrochromic display device according to any of the preceding claims wherein the electrolyte comprises a substance selected from the group consisting of an ionic solid in liquid solution, an ionic liquid, an ionic solid in solid solution, an ionic liquid constrained within the pores of a solid polymer film, and an ionic solid in liquid solution that is constrained within the pores of a solid polymer film.