Patent Publication Number: US-8988757-B2

Title: Low vapor pressure solvent for electrochromic devices

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent application is related to commonly-owned U.S. patent application Ser. No. 10/974,251 entitled “Multi-Color Electrochromic Device”, filed on Oct. 27, 2004 and issued as U.S. Pat. No. 7,450,294 on Nov. 11, 2008; to commonly-owned U.S. patent application Ser. No. 10/974.240 entitled “Dimming Control System for an Array of Electrochromic Devices”, filed on Oct. 27, 2004, and published as U.S. 20050200934 on Sep. 15, 2005, now abandoned; and to U.S. Pat. No. 6,747,780, entitled “Electrochromic Organic Polymer Syntheses and Devices Utilizing Electrochromic Organic Polymers,” Xu et al., issued Jun. 8, 2004; which applications are hereby incorporated by reference. 
     PRIORITY CLAIM 
     This non-provisional patent application claims priority from U.S. Provisional Application No. 60/552,453, filed on Mar. 12, 2004; from U.S. Provisional No. 60/552,606, filed on Mar. 12, 2004, which provisional applications are incorporated herein by reference. 
    
    
     PARTIES TO A JOINT RESEARCH AGREEMENT 
     The Boeing Company and the University of Washington are parties to a Joint Research Agreement. 
     FIELD OF THE INVENTION 
     This invention relates generally to electrochromic devices that exhibit different colors as a function of an applied voltage, and more specifically, to electrolytes for electrochromic devices. 
     BACKGROUND OF THE INVENTION 
     Electrochromic devices are often used as windows, shades, dividers, mirrors, or electronic displays, that change color or degree of opacity in respect to an applied electric field or current. Such an electrochromic device typically is a multi-layer assembly. Outer layers of the electrochromic device typically are electrodes that are optically clear [i.e. substantially transparent or translucent to light in wavelengths of the visual spectrum or at other desired wavelengths, albeit in some instances bearing a limited tint or color]. At least one electrochromic layer is sandwiched between the electrodes. This layer is able to change color or opacity in response to changes in the applied electric field or current to create visual effects. The electrochromic layer is often an organic polymer film or an inorganic thin film of an electrochromic material. When the voltage is applied across the outer conductors, ions in an electrolyte typically move to the electrochromic layer causing the electrochromic material to change color states. Reversing the voltage moves ions away from the electrochromic layer, restoring the device to its previous state. 
     An electrolyte is often used in an electrochromic device to act as a reservoir for the ions that activate the electrochromic layer and/or provide a medium for transporting ions between a separate ion reservoir material or counter-electrode and the electrochromic layer. A salt such as lithium perchlorate (LiClO 4 ) or trifluorosulfonimide (LiN(CF 3 SO 2 ) 2 ) may be used to provide the ions to activate and deactivate the electrochromic layer. The salt is typically dissociated in a solvent in the electrolyte, freeing the ions for use in activating the electrochromic layer. 
     Gel electrolytes in electrochromic devices are often preferred because they are less likely to leak than liquids and more stable dimensionally. One gel electrolyte usable in a preferred electrochromic device includes a solid polymer matrix, especially of polymethylmethacrylate (PMMA). 
     It is desirable for the electrolyte to have high ionic conductivity, permitting the ions to move within the electrolyte, while having relatively low electric conductivity so that the electrochromic device does not short out. Prior art solvents for electrolytes for electrochromic devices include acetonitrile and/or ethylene carbonate. However, many of the solvents used for electrochromic devices have comparatively high vapor pressures and are comparatively volatile and thus can evaporate, and/or are unstable, have higher flammability, and/or have higher toxicity. Evaporation of a solvent in an electrolyte can change the electrolyte composition and degrade functionality of the electrochromic device. 
     SUMMARY OF THE INVENTION 
     The present invention provides an electrolyte for electrochromic devices, the electrolyte comprising γ-butyrolactone (gamma-butyrolactone or GBL). The electrolyte may further include polymethylmethacrylate. The electrolyte may further include a salt, such as a salt that includes lithium perchlorate and/or trifluorosulfonimide. In accordance with further aspects to the invention, the electrolyte may include propylene carbonate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred and alternate embodiments of the present invention are described in detail below with reference to the following drawings. 
         FIG. 1  is an exploded isometric view of an aircraft window incorporating an electrochromic device. 
         FIG. 2A  is a perspective view of an aircraft interior incorporating a multi-color electrochromic device (shown in an inactivated transparent state) as a compartment divider. 
         FIG. 2B  is a perspective view of an aircraft interior incorporating a multi-color electrochromic device exhibiting a logo (shown in an activated colored state). 
         FIG. 3A  is an exemplary electrochromic device incorporating an exemplary γ-butyrolactone (gamma-butyrolactone or GBL) electrolyte in a deactivated state. 
         FIG. 3B  is an exemplary electrochromic device including an exemplary GBL electrolyte in an activated state. 
         FIG. 4A  is an enlargement of an exemplary interface between an electrochromic layer and an exemplary GBL electrolyte, with the electrochromic layer in a deactivated state. 
         FIG. 4B  is an enlargement of an exemplary interface between an electrochromic layer and an exemplary GBL electrolyte, with the electrochromic layer in an activated state. 
         FIG. 5  is a chart of ionic conductivity of exemplary gel electrolytes over time. 
         FIG. 6  is a cross-section of an exemplary electrochromic aircraft window incorporating an exemplary GBL electrolyte. 
         FIG. 7  is a plan view of an exemplary multi-color electrochromic panel exhibiting a pattern. 
         FIG. 7A  is an enlarged view of a section of the electrochromic panel of  FIG. 7  showing exemplary interspersed pixels of a multi-color electrochromic layer. 
         FIG. 8  is a cross-section of an exemplary multi-color electrochromic device. 
         FIG. 9  is a cross-section of deposition of a multi-color electrochromic layer on a substrate. 
         FIG. 10  is a perspective view of an aircraft interior incorporating a multi-color electrochromic device exhibiting a pattern (shown in an activated colored state). 
         FIG. 11  is a schematic view of a window dimming system. 
         FIG. 12  is a schematic view of an alternate window dimming system. 
         FIG. 13  is a side elevational view of an aircraft in accordance with an alternate embodiment of the present invention. 
         FIG. 14  shows a top elevational view of a representative passenger aircraft floor plan incorporating an embodiment of the present invention. 
         FIG. 15A  shows an end cross-sectional view of a passenger aircraft section incorporating an embodiment of the present invention. 
         FIG. 15B  shows an end cross-sectional view of an alternate passenger aircraft section similar to  FIG. 15B . 
         FIG. 16  is a front elevational view of a window assembly incorporating an electrochromic device. 
         FIG. 17  is an exploded isometric view of the window assembly of  FIG. 16 . 
         FIG. 18  is a partial cross-sectional view of the window assembly  FIG. 16 . 
         FIG. 19  is an exploded isometric view of another window assembly that includes an electrochromic device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Detailed Description 
     The present invention relates to electrochromic devices. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 1-19  to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, and that the present invention may be practiced without several of the details described in the following description. 
     Embodiments of the present invention may include a γ-butyrolactone (gamma-butyrolactone or GBL) bearing electrolyte for electrochromic panels. In one embodiment, a GBL electrolyte exhibits high ionic conductivity, high transmittance of light, and stability over time and temperature. These features are useful, for example, in aircraft applications such as electrochromic shades for aircraft windows, replacing hand pulled window shades. 
     This application incorporates by this reference Xu et al.,  Electrochromic Organic Polymer Synthesis and Devices using Electrochromic Organic Polymers , U.S. Pat. No. 6,747,780 B2, issued Jun. 8, 2004; Xu, C., Liu, L., Legniski, S., Le Guilly, M., Taya, M., Weidner, A.,  Enhanced Smart Window Based on Electrochromic Polymers , Smart Structures and Materials 2003: Electroactive Polymer Actuators and Devices (EAPAD), edited by Bar-Cohen, Y., Proceedings of the SPIE, Volume 5051, pp. 404-411 (July, 2003) (hereinafter “Reference A”); Xu, C., Liu, L., Legniski, S., Le Guilly, M., Taya, M,  Gel Electrolyte Candidates for Electrochromic Devices  ( ECD ), Smart Structures and Materials 2004, Electroactive Polymer Actuators and Devices (EAPAD), edited by Bar-Cohen, Y., Proceedings of the SPIE, Volume 5385, pp. 319-325 (July, 2004) (hereinafter “Reference B”); and Liu, L., Xu, C., Legniski, S., Ning, D., M., Taya, M,  Design of Smart Window based on Electrochromic Polymers: New Derivatives of  3,4- alkylenedioxythiophene , Electroactive Polymer Actuators and Devices (EAPAD), edited by Bar-Cohen, Y., Proceedings of the SPIE, Volume 5385, pp. 454-460 (July, 2004) (hereinafter “Reference C”). 
       FIG. 1  is an exploded view of an exemplary electrochromic device used as an aircraft window shade  5  in accordance with an embodiment of the present invention. A structural window  40  is installed in an aircraft fuselage wall  60  with a seal  30 . Inboard of the structural window  40  is a safety backup pane  20 . An electrochromic shade  10  is held in place between the safety pane  20  and an aircraft interior window molding  50  surrounding the window on the interior of the aircraft. When the electrochromic shade  10  is activated, it changes color and/or opacity states, typically either dimming or brightening the aircraft interior by controlling entry of light from outside the aircraft. 
     Turning to  FIG. 2A , a multi-color electrochromic panel  210  in accordance with an embodiment of the invention is shown positioned as a part of a cabin compartment divider  220  in the interior  200  of a passenger aircraft. In  FIG. 2A , the panel  210  is shown in the non-activated state, where it is substantially transparent, permitting viewing through the panel  210 . The multi-color electrochromic panel  210  is held by, and forms a part of, the passenger compartment divider  220  that divides different segments of the passenger compartment from each other. When the electrochromic display  210  is substantially transparent as shown in  FIG. 2A , viewing is permitted through the divider  220 . In vehicular applications, for example, viewing through the divider  220  may be desirable for loading and unloading purposes, regulatory, or safety reasons. 
     In some embodiments, a control panel may be programmed to change the opacity of the electrochromic display  210  to change the environment based upon time of day, the status of the flight (take-off, landing, etc.), or other criteria. Alternately, the electrochromic display  210  may be programmed to change state when a sufficient amount brightness level is sensed within the cabin. An exemplary display  210  in a vehicle or any other environment may thus change with time, at certain times, or during certain events. The display  210  may thus adjust the natural lighting in the interior  200  of the aircraft, or any other vehicle or architectural environment. The display  210  may also be used in a combination with a window, in addition to forming a divider  220 . 
       FIG. 2B  shows a passenger aircraft cabin interior  300  similar to that in  FIG. 8A . An embodiment of a multi-color electrochromic panel  310  is installed in the cabin interior  300  as a part of a cabin compartment divider  320 . In  FIG. 2B , the panel  310  is shown in the activated state exhibiting a multi-color logo  330 . In an activated state, the panel  310  displays the logo  330 , and passengers cannot see through the panel  310 , visually dividing the passenger compartments. In a non-activated state, the multi-color logo  330  disappears and the panel  310  is transparent, in the manner shown in  FIG. 2A . 
       FIG. 3A  shows an exemplary electrochromic device  405  in cross-section in accordance with an embodiment of the invention in a deactivated state  461 . The device  405  includes a first transparent electrode  410  and a second transparent electrode  440 . Disposed between the first electrode  410  and the second electrode  440 , and adjacent to the first electrode  410  is an electrochromic layer  420 . The electrochromic layer  420  in this example changes color or darkens when it is in a reduced state. By way of example, but not limitation, the electrochromic layers may include a polymer film such as poly[3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine] (PProDOT-(CH 3 ) 2 ). 
     As further shown in  FIG. 3A , positioned between the electrochromic layer  420  and the second electrode  440  is an electrolyte layer  430  including an embodiment of a γ-butyrolactone (gamma-butyrolactone or GBL) gel electrolyte (GBL electrolyte)  431 . The GBL electrolyte  431  may include GBL and a salt that when dissociated activates the electrochromic layer  420  with the application of an electric field. GBL (C 4 H 6 O 2 ) is an essentially colorless cyclic ester with a comparatively low vapor pressure capable of performing as a solvent for the salt. Depending upon the desired application, other known electrolytes suitably may be included in the electrolyte layer  430 . 
     An electric field (not shown) is applied to the electrochromic layer  420  and the GBL electrolyte  431  to activate and deactivate the electrochromic layer  420 . In this embodiment, the electric field is provided by an electrical power source  460  connected to the first electrode  410  and the second electrode  440 . The first electrode  410  and the second electrode  440  may suitably include glass, acrylic or polycarbonate coated with Indium Tin Oxide (ITO) to form transparent sheet electrodes. Other transparent materials, other electrode materials, and other configurations including small scale printed circuitry grids may suitably be substituted for ITO coated transparent electrodes. In  FIG. 3A , the first electrode  410  is connected to the positive pole of the voltage source  460  and the second electrode  440  is connected to the negative pole of the electrical source  460 . As further described with reference to  FIGS. 4A and 4B , in this configuration, with a positive charge applied to the first electrode  410 , the electrochromic layer  420  becomes deactivated and substantially transparent. The first electrode  410 , the second electrode  440 , and the GBL electrolyte  431  are also substantially transparent, and thus the electrochromic device  405  in this state as a whole is substantially transparent. 
     The term transparent or colorless should not be limited to mean perfectly transparent (i.e. 100% transmissive) or perfectly colorless, but rather, should be read to include conditions of partial or imperfect transmissivity or substantial translucence. The terms transparent or colorless include being substantially optically clear and transmissive in the visual color frequencies of light, like ordinary glass, or having the property of transmitting visual light (or other desired frequencies, as desired) so that objects lying beyond are visible. 
     In  FIG. 3B , the electrochromic device  405  of  FIG. 3A  is connected to a reversed electrical source  462 . The negative pole of the reversed electrical source  462  is connected to the first electrode  410 , and the positive pole of the reverse electrical source  462  is connected to the second electrode  40 . In this configuration, the electrochromic layer  420  changes to an activated state  463 , substantially darkens, and thus is no longer substantially transparent. As described with reference to  FIGS. 4A and 4B , the reversed electric field (not shown) provided by the reversed electrical source  462  draws positive ions (not shown) from the GBL electrolyte  431  into interaction with the electrochromic layer  420 , thereby activating the electrochromic layer  420 . In many electrochromic devices, it is not necessary to maintain the electric field or the reversed electric field to maintain the color or transparency of the device, only to change the color state or transparency. 
       FIGS. 4A and 4B  are enlarged symbolic diagrams of an exemplary interface  400  such as in  FIGS. 3A and 3B , between an electrochromic layer  420  and a GBL-bearing gel electrolyte  431  (GBL electrolyte), with the electrochromic layer  420  in a one of its operative states  461  in  FIG. 4A , and in a second operative state  463  in  FIG. 4B . In this embodiment, the GBL electrolyte  431  includes a lithium perchlorate salt that dissociates in the GBL bearing electrolyte  430  into perchlorate ions  433  and lithium ions  435 . The GBL acts as a solvent dissociating the lithium perchlorate salt into its component ions. As shown in  FIG. 4A , while not intending to be bound by theory, in the presence of an electric field, with a positive pole  465  adjacent to and outside of the electrochromic layer  420  side of the interface  400 , and a negative pole  467  adjacent to and outside of the GBL electrolyte  431  side of the interface  400 , the perchlorate ions  433  in the GBL electrolyte  431  are drawn toward the electrochromic layer  420 . This permits the electrochromic layer  420  to gain or maintain an oxidized state, and thus gain or maintain a substantially transparent or non-activated state. Alternately, the lithium ions  435  in the GBL electrolyte  431  are drawn away from the electrochromic layer  420  (towards the negative pole  467 ), and thus do not activate the electrochromic layer  420 . 
     In  FIG. 4B , the electric field is reversed from that in  FIG. 2A . The negative pole  467  is adjacent to and outside of the electrochromic layer  420 , and the positive pole  465  is adjacent to and outside of the GBL electrolyte  431 . In this configuration, and again while not intending to be bound by theory, the interface  400  has lithium ions  435  drawn toward the electrochromic layer  420 , or towards the negative pole  467  of the electric field, activating the electrochromic layer  420 , changing its color state, in this instance substantially darkening it. An electrochromic layer  420  that is activated (in this example in a reduced state) when it forms or is adjacent a cathode or the negative pole of an electric field is a cathodic electrochromic layer. Electrochromic layers may also be anodic, and thus are activated when they form or are adjacent the anode or positive pole of an applied electric field. A GBL electrolyte  431  of the present invention may be used with both cathodic and anodic electrochromic layers. 
     A GBL electrolyte  431  advantageously dissociates and carries the lithium ions  435  and the perchlorate ions  433  while having a comparatively low vapor pressure, and comparatively low toxicity and low flammability as compared to other electrolytes. The GBL in a GBL electrolyte  431  acts as a solvent, disassociating the lithium perchlorate, triflourosulfonimide, another suitable salt, or mixtures thereof to allow ions to activate the electrochromic layer. A gelled GBL electrolyte  431  includes an effective amount of polymethylmethacrylate or other suitable colorless gelling agent. The GBL may also be mixed with one or more additional solvents such as ethylene carbonate, propylene carbonate, other higher molecular weight cyclic esters, or other suitable compounds that are essentially colorless, comparatively non-toxic, and have comparatively low volatility. 
     By way of example, but not limitation, propylene carbonate as a second solvent may suitably be mixed with GBL in a GBL-bearing electrolyte  130 . In another embodiment, a suitable GBL-bearing electrolyte  130  includes approximately 70% by weight GBL, 20% by weight propylene carbonate, 3% by weight lithium perchlorate, and 7% by weight polymethylmethacrylate. The weight percentages of the components of this embodiment can vary and still maintain functionality. In some embodiments, the propylene carbonate percentage may be reduced to near 0%, resulting in decreased volatility, but typically higher cost as GBL typically is more expensive than propylene carbonate. Alternately, the weight percentage of propylene carbonate also may be increased to over 20% maintaining functionality, but increasing volatility. Additional quantities of lithium perchlorate may provide additional ions beyond those used in the electrochromic reactions, but typically do not otherwise affect functionality. Considerably smaller weight percentages of lithium perchlorate may decrease color changes in the electrochromic layer. In an alternate embodiment, for example, lithium perchlorate may be substituted or supplemented with the salt trifluorosulfonimide at approximately 3% by weight. 
     The weight percentage of polymethylmethacrylate may also vary, affecting the viscosity of the GBL-bearing electrolyte  130 , but not otherwise affecting the functionality of the electrolyte. Some electrochromic devises use essentially liquid electrolytes with little gelling material or polymethylmethacrylate. Considerably larger quantities of polymethylmethacrylate may cause cloudiness in the electrochromic device. 
     GBL has a vapor pressure of approximately 1.5 mm of Hg at 20° C. Compared to higher vapor pressure solvents such as acetonitrile (ACN) with a vapor pressure of 72.8 mm of Hg at 20 C., GBL suitably has lower rates of diffusion and evaporation from electrochromic devices. GBL suitably exhibits high ionic conductivity, high transmittance of light, and stability over time and temperature. The low viscosity of the GBL provides an ionic environment that facilitates high ionic mobility of the salts activating and deactivating the electrochromic layer. In an example embodiment of a GBL bearing electrolyte  130 , an electronic grade GBL is used and the GBL is dried over molecular sieves to remove any residual water. 
     GBL may suitably have a high ionic conductivity, resulting in a low activation energy facilitating ionic movement. The activation energy for an exemplary gel electrolyte, including GBL, propylene carbonate, lithium perchlorate, and polymethylmethacrylate are approximately 9.7 kJ/mol. ACN as an electrolyte, by way of comparison, has an activation energy of 83 kJ/mol. 
     As shown in  FIG. 5 , an exemplary GBL-bearing electrolyte over time exhibits a stable comparatively high ionic conductivity. As shown in  FIG. 3 , ACN bearing electrolytes exhibit a high initial conductivity (mS/cm), but their ionic conductivity declines over a course of 90 days. Exemplary GBL gel electrolytes including lithium perchlorate exhibit a slightly lower ionic conductivity, but exhibit stable ionic conductivity over 100 days. Thus, a GBL-bearing electrolyte  130  of the present invention suitably provides stable ionic conductivity over time, and thus may increase the lifetime of an electrochromic device. 
       FIG. 6  shows a cross section of an electrochromic device used as a window or shade  500  installed in an aircraft fuselage  580 . The window  500  includes a GBL electrolyte  530  that suitably provides comparatively low flammability and toxicity for aircraft or automotive applications. The window  500  is a multi-layer assembly  505 , including a first electrode  510 , an electrochromic layer  520 , a GBL electrolyte  530 , and a second electrode  540 . The assembly  505  is suitably held in a frame  570 , in this example, adapted to hold the electrochromic window  500  in the wall of an aircraft fuselage  580 . A GBL electrolyte  530  bearing electrochromic window  500  suitably provides ionic conductivity and stability, while complying with appropriate safety limitations for an aircraft application. The GBL electrolyte  530  suitably permits the salt ions  535  within the GBL electrolyte  530  to activate and deactivate electrochromic layer  520  in an aircraft environment through multiple cycles. Structural window layers may be added to the window  500 , leaving the window  500  to serve as a shade. 
     Electrochromic devices of the present invention may also include multi-color electrochromic panels, i.e., polychromatic, having at least two pigments of electrochromic materials. For example,  FIG. 7  shows an exemplary multi-color electrochromic panel  605  in accordance with an embodiment of the present invention. The panel  605  includes three color zones, a first color zone  610 , a second color zone  620 , and a third color zone  630  arranged in the panel  605  in a design or pattern  607 . Alternate color panels  605  suitably may have only one color zone, or a greater number of color zones. The pattern  607  in this embodiment is a colored wave pattern adapted to match or complement other designs, architectural features, patterns or colors in an area (not shown) where the panel  605  is installed, such as described further with reference to  FIG. 10 . The electrochromic device  605  is shown with the electrochromic layer activated to be in an opaque or colored state, as opposed to a substantially transparent state. In a non-activated state, this exemplary panel  605  would be substantially transparent, i.e., the zones  610 ,  620 , and  630  would all be substantially transparent, and the pattern  607  would not be visible. In some embodiments, the pattern  607  may still permit an observer to see partially, or dimly, through the panel  605 , even when the panel  605  is in a fully activated state. 
       FIG. 7A  shows an enlargement of a typical section of an electrochromic layer  650  at an interface  625  between the second color zone  620 , and third color zone  630  of the panel  605  of  FIG. 7  at a pixel level. The electrochromic layer  650  is divided into a plurality of pixels  640 . In this example, the pixels  640  are a uniform size and shape, are square and are of a size such that when viewed from ordinary human viewing distances of approximately two feet or greater, the pixels  640  blend to form colors. The colors formed are based upon the respective areal color densities or percentages of different colors of electrochromic materials in the pixels  640 . In this example, the pixels  640  include varying densities of three colors of electrochromic material, a first color electrochromic material  641 , a second color electrochromic material  643 , and a third color electrochromic material  645 . In this embodiment, the second color zone  620  of the panel  605  of  FIG. 7  is composed of pixels of the third color electrochromic material  645 , while the third color zone  630  is composed of a mixture of pixels of the first color electrochromic material  641  and the second color electrochromic material  643 . By varying the areal percentage or density of pixels  640  of color electrochromic materials  641 ,  643 , and  645 , a wide variety and gradations of colors may be generated from the visual mixing of the pixels  640 . When viewed by the human eye from normal viewing distances, pixels  640  of the first color electrochromic material  641 , the second color electrochromic material  643 , and the third color electrochromic material  645  blend into a desired configuration of varied and graduated colors. Suitable pixel sizes for partial wall size multi-color electrochromic panels  605  include pixels approximately one millimeter square. In single color areas intended to display an unmixed color of an electrochromic material, such areas may have much larger pixels or be aggregated into a single area wide “pixel.” 
     By way of example, but not limitation, electrochromic materials when activated can form various colors that can be mixed visually in a multi-color electrochromic panel  605  as described with reference to  FIG. 7  and  FIG. 7A . For example, 3,3-Dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (1) forms a blue color when activated in a reduced state, and otherwise is substantially transparent. Similarly, 6,6-dimethyl-6,7-dihydro-2H,5H-4,8-dioxa-2-aza-azulene (2) in an activated or reduced state forms a red color and is otherwise substantially transparent. Other colors of electrochromic materials are available and/or under development. Red and blue color electrochromic materials may be combined in various ratios to produce reds, blues, and purples. Red, blue, and green pixels will be able to be combined to form a very wide pallet of colors, as may cyan, magenta, and yellow electrochromic materials. 
     Overlapping of colors, either on a substrate or in a multiple-activated-layer sandwich, may also produce further colors or variable colors as each or multiple color layers are activated (see, e.g., Reference C). By way of example, red, purple, blue, substantially transparent, and black colors suitably may be displayed by activating one or both of the red and blue electrochromic materials to varying intensities either together, separately, or not at all, with a combination of red or blue electrochromic materials. Alternately, applying a segmented activating charge to a display  605 , thus providing different charge regimes to differing subsets and combination of pixels  640  or sections of the display  605 , similarly will also produce a variety of combinations of colors, transparency, and opacity, from the display  405  at different times. 
       FIG. 8  shows a cross-section of an exemplary single electrochromic layer multi-color electrochromic panel  705 . The panel  705  has a first transparent substrate  710 , upon which is deposited a transparent electrical conductor  720 . Deposited on the transparent electrical conductor  720  is an electrochromic layer  730  including areas of a first color electrochromic material  731 , areas of a second color electrochromic material  733 , and areas of a third color electrochromic material  735 . The transparent electrical conductor  720  permits an electrical charge or field to be applied to the color electrochromic materials  731 ,  733 , and  735 . As described above, the areas of the first material  731 , the second material  733 , and the third material  735  are suitably small enough that when activated and viewed from normal viewing distance the colors blend visually to form different areas on the panel  705  where different colors may be displayed. Adjacent to the electrochromic layer  730  is a gel electrolyte layer  740  that conducts, and to some degree stores, ions that activate and deactivate the electrochromic layer  730 . In some embodiments of the present invention, the gel electrolyte includes GBL. 
     The example panel  705  may also incorporate an ion storage layer  750  with a conductor grid  760  that, in some embodiments, comprises a grid including gold (Au). The ion storage layer  750  suitably attracts and stores the oppositely charged counterparts to the ions activating and deactivating the electrochromic layer  730 . 
     In operation, an electrical charge may be provided to the ion storage layer  750  and the grid  760  by a second transparent electrical conductor  780  mounted on a second transparent substrate  770 . 
     In  FIG. 9  a colored electrochromic material  811  is deposited onto a transparent electrical conductor  820  on a transparent substrate  830 , during preparation of an exemplary multi-color electrochromic layer. Masks  810  and  815  cover separate, selected portions  812  and  816 , respectively of the conductor  820 . A third portion of the conductor  813  is unmasked, permitting a jet  809  of electrochromic material  808  (e.g. unpolymerized electrochromic material) to be jetted from a nozzle  807  of a spray device  805 . The first mask  810  and the second mask  815  may subsequently be removed, and the spray device  805  used to direct a jet of alternate color electrochromic materials (not shown) onto the transparent electrical conductor  820  in the previously masked portions  812  and  816  of the conductor  820 . Suitable masking materials include, for example, ablative masking materials such as polyimide. 
     In this embodiment, when the jet  809  of electrochromic material  808  is sprayed toward the unmasked portion  813  of the transparent electrical conductor  820 , the electrochromic materials  808  is electropolymerized by an electrical charge applied to the conductor  820 . At the time of spraying, the materials  808  polymerize on contact with the charged conductor  820 . Alternately, for example, a separate screen mask may be used in lieu of ablative or removable masking materials  810  and  815 . Furthermore, in alternate embodiments, with a defined delivery quantity and a shaped jet  808 , different areas of the transparent electrical conductor  820  may be coated with a colored electrochromic material without utilizing a separate mask. 
       FIG. 10  shows an exemplary aircraft interior  900  similar to that shown in  FIGS. 2A and 2B , with a multi-color electrochromic panel  910  installed in a passenger compartment divider  920 . In this embodiment, the panel  910 , when activated (as shown here) displays a color coordinated interior design or pattern  930  that may be coordinated with and visually match other portions of the compartment divider  920 , which may have a similar, but non-electrochromic interior design or pattern  931 . When the electrochromic panel  910  is in a non-activated state the panel  910  is substantially transparent. Multi-color panels  910 , such as that shown in  FIG. 10 , suitably may have color patterns to match a wide variety of architectural details, designs, patterns, and colors and be used in vehicles, buildings, signs, or the like. 
     Additional embodiments of the present invention include systems and methods for controlling arrays of electrochromic devices. These may include window dimming control systems, such as for the windows of passenger cabins of large commercial transport aircraft. In one embodiment, a control system uses existing wiring to distribute electronic control signals to the windows throughout the passenger cabin. By doing so, much of the weight and cost of wiring for the electrochromic devices are avoided. 
       FIG. 11  is a schematic view of a window dimming system  1000  in accordance with another embodiment of the present invention. In this embodiment, the window dimming system  1000  includes at least one cabin attendant control panel  1002  operatively coupled to a first zone  1010  and a second zone  1020 . Each zone  1010  and  1020  includes a zone control box  1012  and  1022 , respectively, operatively coupled to the cabin attendant control panel  1002  and to a power source  1030 . Also, each of the first and second zones  1010  and  1020  includes a plurality of lighting control modules  1014  and  1024  respectively, which are in turn operatively coupled to a plurality of passenger control panels  1049 . The passenger control panels  1049  are separately connected to an associated electrochromic device  1050 . 
     Although  FIG. 11  depicts the cabin attendant control panel  1002  and the passenger control panels  1049  as being coupled to the electrochromic devices  1050  via conductive members (e.g. wires), in alternate embodiments, the control panels  1049 ,  1002  may be operatively coupled to the electrochromic devices  1050  in a wireless manner using, for example, radio signals or other electromagnetic signals. For example, the cabin attendant control panel  1002  suitably may be incorporated into a portable remote control unit carried by the attendant. Alternately, multi-way switching circuits may also be used, allowing a selection of electrochromic devices  1050  to control. 
     In operation, each of the passenger control modules  1049  may be adjustably controlled (e.g. by a passenger) to vary the color or opacity of its associated electrochromic device  1050 , as described more fully below. Each zone control box  1012  and  1022  is adapted to receive control data  1003  from the cabin attendant control panel  1002 , and responsible for relaying those control commands to the appropriate electrochromic device  1050 . The passenger control modules  1049  may be controlled or overridden by the control data  1003  output from the cabin attendant control panel  1002 , leaving the attendants in control of lighting, for example, for safety reasons. 
     In the embodiment shown in  FIG. 11 , one passenger control module  1049  is coupled to each electrochromic device  1050 . This arrangement may be suitable, for example, for providing each window seat on the aircraft with a passenger control module  1049 . In alternate embodiments, however, a plurality of passenger control modules  1049  may be coupled to each electrochromic device  1050 , such as, for example, the other seats in the same row. In such alternate embodiments, a hierarchy of control authority may be established between the plurality of passenger control modules  1049 , such as, for example, descending control authority with increasing distance from the respective window. 
     The window dimming control system  1000  advantageously provides improved control authority over the opacity of the plurality of electrochromic devices  1050 . For example, in one mode of operation, each passenger within a cabin of the commercial aircraft may be permitted to control the opacity of his or her electrochromic device  1050 , and thus, the tint, color, or transparency of his or her window, using the associated passenger control module  1049 . In an alternate mode of operation, however, a cabin attendant or other authorized person may be permitted to override the settings of the individual passengers using the cabin attendant control panel  1002  as necessary (e.g. during an in-flight movie, during takeoff and landing, etc.) to control the uniformity of the lighting within the passenger cabin. 
     The cabin attendant control panel  1002  may be adapted to provide control authority over the electrochromic devices  1050  in a wide variety of ways. For example, the cabin attendant control panel  1002  may address one, several, all, or any other desired combination of the electrochromic devices  1050 . The control panel  1002  may be programmable or include control options to be selected for the situation. The cabin attendant control panel may include or be linked to a computer processor  1007  providing for computerized or automated control of the electrochromic devices  1050 . For example, in one particular embodiment, the cabin attendant control panel  1002  through the processor  1007  may be programmed to change the opacity of all electrochromic devices  1050  to change the environment based upon time of day, the status of the flight (take-off, landing, etc.), or other criteria. Alternately, the control panel  1002  might be programmed to change state automatically when a sufficient amount of light is sensed within the cabin. On the other hand, the attendant may utilize the cabin attendant control panel  1002  to override the passenger control modules  1049  of a particular passenger (e.g. a particular window seat) or a selected group of passengers (e.g. a selected group of window seats) as necessary for a desired lighting condition. 
     In one representative embodiment, the window dimming system  1000  is operated by means of the lighting control modules  1014  and  1024  and the cabin attendant control panel  1002  (via the first and second zone boxes  1012  and  1022 ) which are adapted to controllably vary the polarity and strength of electric fields powered by the power source  1030 . By positioning the electrochromic devices  1050  adjacent the windows of the aircraft, the opacity of the electrochromic devices  1050  may be controllably varied to lighten or darken the windows of the aircraft. 
     The electrochromic device  1050  may assume a wide variety of embodiments and including those other than described above and shown in  FIGS. 1 and 2A . The invention described above with reference to  FIG. 11  should not be construed to being limited to any particular electrochromic device  1050 , and indeed may be utilized with any electrically controlled shade. Furthermore, in alternate embodiments, electrochromic devices in accordance with the present invention need not be coupled to a surrounding structure (e.g. the aircraft fuselage  280  in  FIG. 1 ). More specifically, in alternate embodiments, the electrochromic devices may be freestanding units. 
     In  FIG. 12 , a window dimming system  1100  includes a cabin attendant control panel  1102  operatively coupled to a first zone  1110  and a second zone  1120 . Each zone includes a zone switch module  1112 ,  1122  operatively coupled to the cabin attendant control panel  1102  and to a power source  1130 . In this embodiment, the zone switch module  1112  controls first and second sub-portions  1111  and  1113  of the first zone  1110 , while the zone switch module  1124  controls the entire second zone  1120 . Also, each of the first and second zones  1110  and  1120  includes a plurality of overhead electronic units  1114  and  1124 , respectively, which are, in turn, each operatively coupled to associated passenger reading lights  1115  and  1125 , respectively. The first zone  1110  further includes a plurality of dimmer controls  1118  operatively coupled to the overhead electronic units  1114  and to an associated electrochromic dimmable window  1119 . The passenger dimmer controls  1118  are located conveniently for the passengers on each seat or row of seats on the armrests, tray tables, seat backs, or interior panels. 
     In operation, each of the dimmable windows  1119  of the first zone  1110  may be adjustably controlled independently of the other dimmable windows  1119  using the associated dimmer control  1118 . Alternately, all of the dimmable windows  1119  may be controlled using the cabin attendant control panel  1102 . The cabin attendant control panel  1102  may have override authority over each of the individual dimmer controls  1118 , and is adapted to simultaneously adjust the electric fields within the plurality of dimmable windows  1119  of the first and second zones  1110 ,  1120  to selectively activate and de-activate the plurality of dimmable windows  1119  of the first and second zones  1110 ,  1120  either independently or in unison (or both). 
     The window dimming control system  1100  advantageously utilizes existing wiring to distribute the desired electronic control signals to the dimmable windows  1120  throughout the passenger cabin of the aircraft. In this way, much of the weight and cost of wiring that would otherwise be dedicated to this task is reduced or eliminated. In one particular embodiment, for example, the dimmer controls  1118  and the associated dimmable windows  1119  are simply incorporated into an existing Cabin Services System (CSS) that controls other functions within the main passenger cabin, including, for example, the reading lights associated with each passenger seat. 
     A wide variety of apparatus may be conceived that include electrochromic device array control systems in accordance with alternate embodiments of the present invention. For example,  FIG. 13  is a side elevational view of an aircraft  1200  having a plurality of window assemblies  1201  and one or more window dimming control systems  1202  formed in accordance with alternate embodiments of the present invention. 
     In general, except for the window dimming control systems  1202  formed in accordance with the present invention, the various components and subsystems of the aircraft  1200  may be of known construction and, for the sake of brevity, will not be described in detail. Embodiments of window dimming control systems  1202  in accordance with the present invention, including but not limited to those embodiments described above and shown in  FIGS. 11-12 , may be employed in any desired location throughout the aircraft  1200 . 
     More specifically, as shown in  FIG. 13 , the aircraft  1200  includes one or more propulsion units  1204  coupled to an airframe (not visible) disposed within a fuselage  1205 , wing assemblies  1206  (or other lifting surfaces), a tail assembly  1208 , a landing assembly  1210 , a control system (not visible)  1212 , and a host of other systems and subsystems that enable proper operation of the aircraft  1200 . A plurality of window assemblies  1201  are distributed throughout the fuselage  1205 , and a plurality of window dimming control systems  1202  in accordance with the present invention are distributed throughout the various portions of the aircraft  1200 , including, for example, within the cockpit ( 1202   a ), the first-class section ( 1202   c ), and the coach or business class section ( 1202   c ). 
     Although the aircraft  1200  shown in  FIG. 11  is generally representative of a commercial passenger aircraft, including, for example, the 737, 747, 757, 767, 777, and 7E7 models commercially available from The Boeing Company of Chicago, Ill., the inventive apparatus and methods disclosed may also be employed in virtually any other types of aircraft. More specifically, the teachings of the present invention may be applied to other types and models of passenger aircraft, fighter aircraft, cargo aircraft, rotary aircraft, and any other types of aircraft, including those described, for example, in The Illustrated Encyclopedia of Military Aircraft by Enzo Angelucci, published by Book Sales Publishers, September 2001, and in Jane&#39;s All the World&#39;s Aircraft published by Jane&#39;s Information Group of Coulsdon, Surrey, United Kingdom, which texts are incorporated herein by reference. Alternate embodiments of apparatus and methods in accordance with the present invention may be used in the other applications, including, for example, ships, buses, trains, recreational vehicles, subways, monorails, houses, apartments, office buildings, or any other desired applications. 
       FIG. 14  shows a top elevational view of a representative passenger aircraft floor plan  1300 . The passenger aircraft floor plan  1300  includes first port and starboard control systems  1310 ,  1311  covering port and starboard portions of the business section, a forward economy section control system  1320 , and second port and starboard control systems  1330 ,  1331  covering the rear economy section. Each of the window control systems shown in  FIG. 14  may include one or more zones such as described above with reference to  FIGS. 11-12 . Clearly, a wide variety of alternate embodiments of passenger aircraft floor plans  1300  having various configurations of window control systems in accordance with the present invention may be conceived. 
     In  FIG. 15A  passenger aircraft section  1400  includes a window control system  1410  having a first or left zone  1411  and a second or right zone  1413 . A master control module  1412  is wirelessly coupled to electrochromic devices  1420  of the window control system  1410 . Passenger control modules  1430  are positioned over the passenger seats  1440 . As further shown in  FIG. 15B , in another embodiment, a passenger aircraft section  1450  includes a control system  1460  adapted to control a freestanding electrochromic display or partition  1475 . A master control module  1462  is located overhead in the aircraft section  1450 . One or more passenger control modules  1480  may be located proximate the seats  1490 , including, for example, within the armrests between the adjacent seats  1490 , or on upper and lateral portions of the aircraft section  1450 . Similarly, the master control module  1462  may be disposed in any desired location. 
     As shown in  FIG. 16  and  FIG. 17 , an exemplary window assembly  1500  includes a window member  1510 , and an electrochromic assembly  1550  disposed adjacent the window member  1510 . A passenger control module  1560  is operatively coupled to the electrochromic assembly  1550 . An edge trim  1514  is disposed about an outer perimeter of the window member  1510 . A power source  1562  provides power to the window assembly  1500 . Bus bars  1581  and  1583  around the perimeter of the electrochromic assembly  1550  provide electrical connections to the assembly  1550 . 
       FIG. 18  is a detailed cross sectional view of an outer perimeter of the electrochromic device  1550  of  FIG. 16 . The device  1550  includes two outer transparent layers, a first outer layer  1551  and a second outer layer  1553  proximate to each other. The outer layers  1551  and  1553  by way of example may include glass, acrylic, or polycarbonate. The outer layers  1551  and  1553  are coated on their interior surfaces by a first transparent electrode coating  1577  and a second transparent electrode coating  1579 , respectively. In a central portion  1552  of the first outer layer  1551 , an electrochromic layer  1561  is deposited on the first electrode coating  1577 . In a central portion  1552  of the second outer layer  1553 , a counter-electrode grid  1565  is deposited on the second electrode coating  1579 . Between the counter-electrode grid  1565  and the electrochromic layer  1561  is a layer of gel electrolyte  1563 . 
     Attached to an edge portion  1554  of the first electrode coating  1571  is a first busbar  1581 . As shown in  FIG. 17 , the first busbar  1581  suitably spans the circumference of the first outer layer  1551 , providing an electrical connection to the first transparent electrode coating  1577 . Attached to an edge portion  1554  of the second electrode coating  1579  is a second busbar  1583 , that as shown in  FIG. 17  suitably spans the circumference of the second outer layer  1553 , providing an electrical connection to the second transparent electrode coating  1579 . The first busbar  1581  and the second busbar  1583  suitably may be any conductor, including by way of example copper strips. A space  1585  is maintained between the first busbar  1581  and the second busbar  1583 , so that charges may be provided to their respective electrode layers  1577  and  1579 , without the first busbar  1581  and second busbar  1583  making contact with each other. The space  1585  may also hold or be filled with a dielectric, providing insulation between the busbars  1581  and  1582 . A first adhesive seal  1571  between the first outer layer  1551  and second outer layer  1553 , between their central portions  1552  and their edge portions  1554 , suitably seals and contains the edge of the electrochromic layer  1561 , the electrolyte  1563 , and the counter electrode grid  1565 , permitting the device to activate and deactivate when an electric charge is applied to the device  1550  through a power source (not shown) electrically coupled with the busbars  1581  and  1583 . A second adhesive seal  1573  seals the outermost edge  1556  of the first outer layer  1551  and second outer layer  1553 , suitably isolating and insulating the busbars  1581  and  1583  from the outside environment. Further, the edge portion  1554  and the outermost edge  1556  of the first outer layer  1551  and the second outer layer  1553  are surrounded by an edge trim  1587 . The edge trim  1587  in this embodiment is in the form of a clip assisting in holding together the components of the device  1550 , including the first outer layer  1551  and the second outer layer  1553 , with the electrode layers  1577  and  1579 , the electrochromic layer  1561 , the electrolyte  1563 , the counter electrode grid  1565 , the two busbars  1581  and  1583  in a fixed configuration between them. 
       FIG. 19  is an exploded isometric view of a window assembly  1600  including a first window member  1610  having a transparent portion  1612  and an edge trim portion  1614 . Similarly, an outer second window member  1620  includes a transparent portion  1622  and a mounting portion  1624 . An electrochromic assembly  1650  is disposed between the first and second window members  1610 ,  1620 . Passenger controls  1660  are disposed within the edge trim portion  1614  of the first window member  1610 , in this example the inner window member for an aircraft, and are operatively coupled to the electrochromic assembly  1650 . The passenger controls  1660 , for example, allow the passenger in the window seat to control the electrochromic assembly  1650  as desired, subject to override signals from a master controller (not shown) as described with reference to  FIGS. 11 and 12 . 
     While preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes may be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred and alternate embodiments. Instead, the invention should be determined entirely by reference to the claims that follow: