Abstract:
An electrochromic variable reflectance mirror for a vehicle includes a front element and a rear element. A seal is provided to sealably bond the elements together in a spaced-apart relationship to define a chamber, and an electrochromic material is disposed in the chamber. The seal comprises an epoxy resin cured with a cycloaliphatic amine. The cycloaliphatic amine may be a bis(cycloaliphatic) amine, or more specifically, bis(aminocyclohexyl) methane (PACM). The epoxy resin may be an epoxy novolac resin such as an epoxy phenolic novolac (e.g., DEN431) or an epoxy cresyl novolac resin, a bisphenol A epoxy resin, a bisphenol F epoxy resin, a tetraglycidyl methylenebisbenzenamine, or a glycidyl benzenamine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of co-pending U.S. patent application Ser. No. 09/994,218, entitled “ELECTROCHROMIC REARVIEW MIRROR INCORPORATING A THIRD SURFACE PARTIALLY TRANSMISSIVE REFLECTOR,” filed on Nov. 26, 2001, by William L. Tonar et al.; which is a continuation of U.S. patent application Ser. No. 09/311,955, filed on May 14, 1999, entitled “ELECTROCHROMIC REARVIEW MIRROR INCORPORATING A THIRD SURFACE METAL REFLECTOR AND A DISPLAY/SIGNAL LIGHT,” by William L. Tonar et al., now U.S. Pat. No. 6,356,376; which is a continuation-in-part of U.S. patent application Ser. No. 09/206,788, filed on Dec. 7, 1998, entitled “ELECTROCHROMIC REARVIEW MIRROR INCORPORATING A THIRD SURFACE METAL REFLECTOR AND A DISPLAY/SIGNAL LIGHT,” by William L. Tonar et al., now U.S. Pat. No. 6,166,848; which is a continuation-in-part of co-pending U.S. patent application Ser. No. 09/197,400, filed on Nov. 20, 1998, entitled “ELECTROCHROMIC REARVIEW MIRROR INCORPORATING A THIRD SURFACE METAL REFLECTOR AND A DISPLAY/SIGNAL LIGHT,” by William L. Tonar et al., now U.S. Pat. No. 6,111,684; which is a continuation-in-part of U.S. patent application Ser. No. 09/114,386, entitled “ELECTROCHOMIC REARVIEW MIRROR INCORPORATING A THIRD SURFACE METAL REFLECTOR,” filed on Jul. 13, 1998 by Jeffrey A. Forgette et al., now U.S. Pat. No. 6,064,508; which is a continuation of U.S. patent application Ser. No. 08/832,587, entitled “ELECTROCHOMIC REARVIEW MIRROR INCORPORATING A THIRD SURFACE METAL REFLECTOR,” filed on Apr. 2, 1997, by Jeffrey A. Forgette et al., now U.S. Pat. No. 5,818,625. Priority under 35 U.S.C. §120 is hereby claimed as to the filing dates of each of these applications. The entire disclosures of each of these applications are incorporated herein by reference.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to electrochromic rearview mirrors for motor vehicles and, more particularly, to improved electrochromic rearview mirrors incorporating third surface reflector/electrode in contact with at least one solution-phase electrochromic material.  
           [0003]    Heretofore, various rearview mirrors for motor vehicles have been proposed which change from the full reflectance mode (day) to the partial reflectance mode(s) (night) for glare-protection purposes from light emanating from the headlights of vehicles approaching from the rear. Among such devices are those wherein the transmittance is varied by thermochromic, photochromic, or electro-optic (e.g., liquid crystal, dipolar suspension, electrophoretic, electrochromic, etc.) means and where the variable transmittance characteristic affects electromagnetic radiation that is at least partly in the visible spectrum (wavelengths from about 3800 Å to about 7800 Å). Devices of reversibly variable transmittance to electromagnetic radiation have been proposed as the variable transmittance element in variable transmittance light filters, variable reflectance mirrors, and display devices which employ such light filters or mirrors in conveying information. These variable transmittance light filters have included windows.  
           [0004]    Devices of reversibly variable transmittance to electromagnetic radiation, wherein the transmittance is altered by electrochromic means, are described, for example, by Chang, “Electrochromic and Electrochemichromic Materials and Phenomena,” in  Non - emissive Electrooptic Displays,  A. Kmetz and K. von Willisen, eds. Plenum Press, New York, N.Y. 1976, pp. 155-196 (1976) and in various parts of  Eletrochromism , P. M. S. Monk, R. J. Mortimer, D. R. Rosseinsky, VCH Publishers, Inc., New York, N.Y. (1995). Numerous electrochromic devices are known in the art. See, e.g., Manos, U.S. Pat. No. 3,451,741; Bredfeldt et al., U.S. Pat. No. 4,090,358; Clecak et al., U.S. Pat. No. 4,139,276; Kissa et al., U.S. Pat. No. 3,453,038; Rogers, U.S. Pat. Nos. 3,652,149, 3,774,988 and 3,873,185; and Jones et al., U.S. Pat. Nos. 3,282,157, 3,282,158, 3,282,160 and 3,283,656.  
           [0005]    In addition to these devices there are commercially available electrochromic devices and associated circuitry, such as those disclosed in U.S. Pat. No. 4,902,108, entitled “SINGLE-COMPARTMENT, SELF-ERASING, SOLUTION-PHASE ELECTROCHROMIC DEVICES SOLUTIONS FOR USE THEREIN, AND USES THEREOF”, issued Feb. 20, 1990, to Harlan J. Byker; Canadian Patent No. 1,300,945, entitled “AUTOMATIC REARVIEW MIRROR SYSTEM FOR AUTOMOTIVE VEHICLES,” issued May 19, 1992, to Jon H. Bechtel et al.; U.S. Pat. No. 5,128,799, entitled “VARIABLE REFLECTANCE MOTOR VEHICLE MIRROR,” issued Jul. 7, 1992, to Harlan J. Byker; U.S. Pat. No. 5,202,787, entitled “ELECTRO-OPTIC DEVICE”, issued Apr. 13, 1993, to Harlan J. Byker et al.; U.S. Pat. No. 5,204,778, entitled “CONTROL SYSTEM FOR AUTOMATIC REARVIEW MIRRORS,” issued Apr. 20, 1993, to Jon H. Bechtel; U.S. Pat. No. 5,278,693, entitled “TINTED SOLUTION-PHASE ELECTROCHROMIC MIRRORS,” issued Jan. 11, 1994, to David A. Theiste et al.; U.S. Pat. No. 5,280,380, entitled “UV-STABILIZED COMPOSITIONS AND METHODS,” issued Jan. 18, 1994, to Harlan J. Byker; U.S. Pat. No. 5,282,077, entitled “VARIABLE REFLECTANCE MIRROR,” issued Jan. 25, 1994, to Harlan J. Byker; U.S. Pat. No. 5,294,376, entitled “BIPYRIDINIUM SALT SOLUTIONS,” issued Mar. 15, 1994, to Harlan J. Byker; U.S. Pat. No. 5,336,448, entitled “ELECTROCHROMIC DEVICES WITH BIPYRIDINIUM SALT SOLUTIONS,” issued Aug. 9, 1994, to Harlan J. Byker; U.S. Pat. No. 5,434,407, entitled “AUTOMATIC REARVIEW MIRROR INCORPORATING LIGHT PIPE,” issued Jan. 18, 1995, to Frederick T. Bauer et al.; U.S. Pat. No. 5,448,397, entitled “OUTSIDE AUTOMATIC REARVIEW MIRROR FOR AUTOMOTIVE VEHICLES,” issued Sep. 5, 1995, to William L. Tonar; and U.S. Pat. No. 5,451,822, entitled “ELECTRONIC CONTROL SYSTEM,” issued Sep. 19, 1995, to Jon H. Bechtel et al. Each of these patents is commonly assigned with the present invention and the disclosures of each, including the references contained therein, are hereby incorporated herein in their entirety by reference. Such electrochromic devices may be utilized in a fully integrated inside/outside rearview mirror system or as separate inside or outside rearview mirror systems.  
           [0006]    [0006]FIG. 1 shows a typical electrochromic mirror device  10 , having front and rear planar elements  12  and  16 , respectively. A transparent conductive coating  14  is placed on the rear face of the front element  12 , and another transparent conductive coating  18  is placed on the front face of rear element  16 . A reflector ( 20   a ,  20   b  and  20   c ), typically comprising a silver metal layer  20   a  covered by a protective copper metal layer  20   b , and one or more layers of protective paint  20   c , is disposed on the rear face of the rear element  16 . For clarity of description of such a structure, the front surface of the front glass element is sometimes referred to as the first surface, and the inside surface of the front glass element is sometimes referred to as the second surface. The inside surface of the rear glass element is sometimes referred to as the third surface, and the back surface of the rear glass element is sometimes referred to as the fourth surface. The front and rear elements are held in a parallel and spaced-apart relationship by seal  22 , thereby creating a chamber  26 . The electrochromic medium  24  is contained in space  26 . The electrochromic medium  24  is in direct contact with transparent electrode layers  14  and  18 , through which passes electromagnetic radiation whose intensity is reversibly modulated in the device by a variable voltage or potential applied to electrode layers  14  and  18  through clip contacts and an electronic circuit (not shown).  
           [0007]    The electrochromic medium  24  placed in space  26  may include surface-confined, electrodeposition type or solution-phase type electrochromic materials and combinations thereof. In an all solution-phase medium, the electrochemical properties of the solvent, optional inert electrolyte, anodic materials, cathodic materials, and any other components that might be present in the solution are preferably such that no significant electrochemical or other changes occur at a potential difference which oxidizes anodic material and reduces the cathodic material other than the electrochemical oxidation of the anodic material, electrochemical reduction of the cathodic material and the self-erasing reaction between the oxidized form of the anodic material and the reduced form of the cathodic material.  
           [0008]    In most cases, when there is no electrical potential difference between transparent conductors  14  and  18 , the electrochromic medium  24  in space  26  is essentially colorless or nearly colorless, and incoming light (I O ) enters through front element  12 , passes through transparent coating  14 , electrochromic containing chamber  26 , transparent coating  18 , rear element  16 , and reflects off layer  20   a  and travels back through the device and out front element  12 . Typically, the magnitude of the reflected image (I R ) with no electrical potential difference is about  45  percent to about  85  percent of the incident light intensity (I O ). The exact value depends on many variables outlined below, such as, for example, the residual reflection (I′ R ) from the front face of the front element, as well as secondary reflections from the interfaces between: the front element  12  and the front transparent electrode  14 ; the front transparent electrode  14  and the electrochromic medium  24 ; the electrochromic medium  24  and the second transparent electrode  18 ; and the second transparent electrode  18  and the rear element  16 . These reflections are well known in the art and are due to the difference in refractive indices between one material and another as the light crosses the interface between the two. If the front element and the back element are not parallel, then the residual reflectance (I′ R ) or other secondary reflections will not superimpose with the reflected image (I R ) from mirror surface  20   a , and a double image will appear (where an observer would see what appears to be double (or triple) the number of objects actually present in the reflected image).  
           [0009]    There are minimum requirements for the magnitude of the reflected image depending on whether the electrochromic mirrors are placed on the inside or the outside of the vehicle. For example, according to current requirements from most automobile manufacturers, inside mirrors must have a high-end reflectivity of at least 70 percent and outside mirrors must have a high-end reflectivity of at least 50 percent.  
           [0010]    Electrode layers  14  and  18  are connected to electronic circuitry which is effective to electrically energize the electrochromic medium, such that when a potential is applied across the transparent conductors  14  and  18 , electrochromic medium in space  26  darkens such that incident light (I O ) is attenuated as the light passes toward the reflector  20   a  and as it passes back through after being reflected. By adjusting the potential difference between the transparent electrodes, such a device can function as a “gray-scale” device, with continuously variable transmittance over a wide range. For solution-phase electrochromic systems, when the potential between the electrodes is removed or returned to zero, the device spontaneously returns to the same, zero-potential, equilibrium color and transmittance as the device had before the potential was applied. Other electrochromic materials are available for making electrochromic devices. For example, the electrochromic medium may include electrochromic materials that are solid metal oxides, redox active polymers and hybrid combinations of solution-phase and solid metal oxides or redox active polymers; however, the above-described solution-phase design is typical of most of the electrochromic devices presently in use.  
           [0011]    Even before a fourth surface reflector electrochromic mirror was commercially available, various groups researching electrochromic devices had discussed moving the reflector from the fourth surface to the third surface. Such a design has advantages in that it should, theoretically, be easier to manufacture because there are fewer layers to build into a device, i.e., the third surface transparent electrode is not necessary when there is a third surface reflector/electrode. Although this concept was described as early as 1966, no group had commercial success because of the exacting criteria demanded from a workable auto-dimming mirror incorporating a third surface reflector. U.S. Pat. No. 3,280,701, entitled “OPTICALLY VARIABLE ONE-WAY MIRROR,” issued Oct. 25, 1966, to J. F. Donnelly et al. has one of the earliest discussions of a third surface reflector for a system using a pH-induced color change to attenuate light.  
           [0012]    U.S. Pat. No. 5,066,112, entitled “PERIMETER COATED, ELECTRO-OPTIC MIRROR,” issued Nov. 19, 1991, to N. R. Lynam et al. teaches an electro-optic mirror with a conductive coating applied to the perimeter of the front and rear glass elements for concealing the seal. Although a third surface reflector is discussed therein, the materials listed as being useful as a third surface reflector suffer from one or more of the following deficiencies: not having sufficient reflectivity for use as an inside mirror, or not being stable when in contact with a solution-phase electrochromic medium containing at least one solution-phase electrochromic material.  
           [0013]    Others have broached the topic of a reflector/electrode disposed in the middle of all solid state-type devices. For example, U.S. Pat. Nos. 4,762,401, 4,973,141, and 5,069,535 to Baucke et al. teach an electrochromic mirror having the following structure: a glass element; a transparent (ITO) electrode; a tungsten oxide electrochromic layer; a solid ion-conducting layer; a single layer hydrogen ion-permeable reflector; a solid ion conducting layer; a hydrogen ion storage layer; a catalytic layer; a rear metallic layer; and a back element (representing the conventional third and fourth surface). The reflector is not deposited on the third surface and is not directly in contact with electrochromic materials, certainly not at least one solution-phase electrochromic material and associated medium.  
           [0014]    Consequently, it is desirable to provide an improved high reflectivity electrochromic rearview mirror having a third surface reflector/electrode in contact with a solution-phase electrochromic medium containing at least one electrochromic material.  
         SUMMARY OF THE INVENTION  
         [0015]    Aspects of the present invention, which will become apparent from the specification as a whole, including the drawings, are accomplished in accordance with the present invention by incorporating a reflector/electrode on the inside (third) surface of a dimming portion of the rearview mirror. This reflector/electrode forms an integral electrode in contact with at least one solution-phase electrochromic material, and may be a single layer of a highly reflective silver alloy or may comprise a series of coatings where the outer coating is a highly reflective silver alloy. When a series of coatings is used for the reflector/electrode, there should be a base coating which bonds to the glass surface and resists any adverse interaction, e.g., corrosive action, with any constituents of the electrochromic medium, an optional intermediate layer (or layers) which bonds well to the base coating and resists any adverse interaction with the electrochromic medium, and at least one highly reflective silver alloy which directly contacts the electrochromic medium and which is chosen primarily for its adequate bond to the peripheral seal, its high reflectance, good shelf life, stable behavior as an electrode, resistance to adverse interaction with the electrochromic medium, resistance to atmospheric corrosion, resistance to electrical contact corrosion, and the ability to adhere to the base or intermediate layer(s), if present. If a single layer of highly reflective silver alloy is utilized, it must also meet these operational criteria.  
           [0016]    In another embodiment of the present invention, when a very thin over-coating is placed over the highly reflective layer, then the highly reflective layer may be silver metal or a silver alloy.  
           [0017]    In yet another embodiment of the present invention, the third surface reflector/electrode includes at least one base layer that is disposed over the entire third surface of the electrochromic mirror. A highly reflective layer is disposed over the central portion of the base layer(s) and not over the perimeter edge portion where the seal will be placed. Optionally, one or more intermediate layers may be disposed between the base and reflective layers, and may be placed over the entire third surface, or may be placed over the central portion or both (if there is more than one intermediate layer).  
           [0018]    The third surface reflector of the present invention may additionally provide for significant improvement of the electrical interconnection techniques used to impart a voltage or drive potential to the transparent conductor on the second surface of the electrochromic mirror. This is accomplished both by providing improved contact stability between the contacts, such as clips, and the reflector layer and by providing unique and advantageous buss bar configurations. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, where like numerals represent like components, in which:  
         [0020]    [0020]FIG. 1 is an enlarged cross-sectional view of a prior art electrochromic mirror assembly;  
         [0021]    [0021]FIG. 2 is a front elevational view schematically illustrating an inside/outside electrochromic rearview mirror system for motor vehicles where the inside and outside mirrors incorporate the mirror assembly of the present invention;  
         [0022]    [0022]FIG. 3 is an enlarged cross-sectional view of the inside electrochromic rearview mirror incorporating a third surface reflector/electrode illustrated in FIG. 2, taken on the line  2 - 2 ′ thereof;  
         [0023]    [0023]FIG. 4 is an enlarged cross-sectional view of an electrochromic mirror incorporating an alternate embodiment of a third surface reflector/electrode according to the present invention;  
         [0024]    [0024]FIG. 5 a  is an enlarged cross-sectional view of an electrochromic mirror having an improved arrangement for applying a drive potential to the transparent conductor on the second surface of the mirror;  
         [0025]    [0025]FIG. 5 b  is an enlarged top view of the third surface reflector of FIG. 5 a ; and  
         [0026]    [0026]FIG. 6 is an enlarged cross-sectional view of an electrochromic mirror using a cured and machine-milled epoxy seal to hold the transparent elements in a spaced-apart relationship.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]    [0027]FIG. 2 shows a front elevational view schematically illustrating an inside mirror assembly  110  and two outside rearview mirror assemblies  111   a  and  111   b  for the driver-side and passenger-side, respectively, all of which are adapted to be installed on a motor vehicle in a conventional manner and where the mirrors face the rear of the vehicle and can be viewed by the driver of the vehicle to provide a rearward view. Inside mirror assembly  110 , and outside rearview mirror assemblies  111   a  and  111   b  may incorporate light-sensing electronic circuitry of the type illustrated and described in the above-referenced Canadian Patent No. 1,300,945, U.S. Pat. No. 5,204,778, or U.S. Pat. No. 5,451,822, and other circuits capable of sensing glare and ambient light and supplying a drive voltage to the electrochromic element. Mirror assemblies  110 ,  111   a , and  111   b  are essentially identical in that like numbers identify components of the inside and outside mirrors. These components may be slightly different in configuration but function in substantially the same manner and obtain substantially the same results as similarly numbered components. For example, the shape of the front glass element of inside mirror  110  is generally longer and narrower than outside mirrors  111   a  and  111   b . There are also some different performance standards placed on inside mirror  110  compared with outside mirrors  111   a  and  111   b . For example, inside mirror  110  generally, when fully cleared, should have a reflectance value of about 70 percent to about 85 percent or higher whereas the outside mirrors often have a reflectance of about 50 percent to about 65 percent. Also, in the United States (as supplied by the automobile manufacturers), the passenger-side mirror  111   b  typically has a spherically bent, or convex shape, whereas the driver-side mirror  111   a  and inside mirror  110  presently must be flat. In Europe the driver-side mirror  111   a  is commonly flat or aspheric, whereas the passenger-side mirror  111   b  has a convex shape. In Japan, both outside mirrors have a convex shape. The following description is generally applicable to all mirror assemblies of the present invention.  
         [0028]    [0028]FIG. 3 shows a cross-sectional view of mirror assembly  110  having a front transparent element  112  having a front surface  112   a  and a rear surface  112   b , and a rear element  114  having a front surface  114   a  and a rear surface  114   b . For clarity of description of such a structure, the following designations will be used hereinafter. The front surface  112   a  of the front glass element will be referred to as the first surface and the back surface  112   b  of the front glass element as the second surface. The front surface  114   a  of the rear glass element will be referred to as the third surface, and the back surface  114   b  of the rear glass element as the fourth surface. Chamber  125  is defined by a layer of transparent conductor  128  (disposed on second surface  112   b ), a reflector/electrode  120  (disposed on third surface  114   a ), and an inner circumferential wall  132  of sealing member  116 .  
         [0029]    Front transparent element  112  may be any material which is transparent and has sufficient strength to be able to operate in the conditions, e.g., varying temperatures and pressures, commonly found in the automotive environment. Front element  112  may comprise any type of borosilicate glass, soda lime glass, float glass or any other material, such as, for example, a polymer or plastic, that is transparent in the visible region of the electromagnetic spectrum. Front element  112  is preferably a sheet of glass. Rear element  114  must meet the operational conditions outlined above, except that it does not need to be transparent, and therefore may comprise polymers, metals, glass, ceramics, and preferably is a sheet of glass.  
         [0030]    The coatings of the third surface  114   a  are sealably bonded to the coatings on the second surface  112   b  in a spaced-apart and parallel relationship by a seal member  116  disposed near the outer perimeter of both second surface  112   b  and third surface  114   a . Seal member  116  may be any material that is capable of adhesively bonding the coatings on the second surface  112   b  to the coatings on the third surface  114   a  to seal the perimeter such that electrochromic material  126  does not leak from chamber  125 . Optionally, the layer of transparent conductive coating  128  and the layer of reflector/electrode  120  may be removed over a portion where the seal member is disposed (not the entire portion, otherwise the drive potential could not be applied to the two coatings). In such a case, seal member  116  must bond well to glass.  
         [0031]    The performance requirements for a perimeter seal member  116  used in an electrochromic device are similar to those for a perimeter seal used in a liquid crystal device (LCD) which are well known in the art. The seal must have good adhesion to glass, metals and metal oxides; must have low permeabilities for oxygen, moisture vapor and other detrimental vapors and gases; and must not interact with or poison the electrochromic or liquid crystal material it is meant to contain and protect. The perimeter seal can be applied by means commonly used in the LCD industry such as by silk-screening or dispensing. Totally hermetic seals such as those made with glass frit or solder glass can be used, but the high temperatures involved in processing (usually near 450° C.) this type of seal can cause numerous problems such as glass substrate warpage, changes in the properties of transparent conductive electrode, and oxidation or degradation of the reflector. Because of their lower processing temperatures, thermoplastic, thermosetting, or UV curing organic sealing resins are preferred. Such organic resin sealing systems for LCDs are described in U.S. Pat. Nos. 4,297,401, 4,418,102, 4,695,490, 5,596,023 and 5,596,024. Because of their excellent adhesion to glass, low oxygen permeability, and good solvent resistance, epoxy based organic sealing resins are preferred. These epoxy resin seals may be UV curing, such as described in U.S. Pat. No. 4,297,401, or thermally curing, such as with mixtures of liquid epoxy resin with liquid polyamide resin or dicyandiamide, or they can be homopolymerized. The epoxy resin may contain fillers or thickeners to reduce flow and shrinkage such as fumed silica, silica, mica, clay, calcium carbonate, alumina, etc., and/or pigments to add color. Fillers pretreated with hydrophobic or silane surface treatments are preferred. Cured resin crosslink density can be controlled by use of mixtures of mono-functional, di-functional, and multi-functional epoxy resins and curing agents. Additives such as silanes or titanates can be used to improve the seal&#39;s hydrolytic stability, and spacers such as glass beads or rods can be used to control final seal thickness and substrate spacing. Suitable epoxy resins for use in a perimeter seal member  116  include but are not limited to: “EPON RESIN” 813, 825, 826, 828, 830, 834, 862, 1001F, 1002F, 2012, DPS-155, 164, 1031, 1074, 58005, 58006, 58034, 58901, 871, 872 and DPL-862 available from Shell Chemical Co., Houston, Tex.; “ARALITE” GY 6010, GY 6020, CY 9579, GT 7071, XU 248, EPN 1139, EPN 1138, PY 307, ECN 1235, ECN 1273, ECN 1280, MT 0163, MY 720, MY 0500, MY 0510 and PT 810 available from Ciba Geigy, Hawthorne, N.Y.; “D.E.R.” 331, 317, 361, 383, 661, 662, 667, 732, 736, “D.E.N.” 431, 438, 439 and 444 available from Dow Chemical Co., Midland, Mich. Suitable epoxy curing agents include V-15, V-25 and V-40 polyamides from Shell Chemical Co.; “AJICURE” PN-23, PN-34 and VDH available from Ajinomoto Co., Tokyo, Japan; “CUREZOL” AMZ, 2MZ, 2E4MZ, C11Z, C17Z, 2PZ, 21Z and 2P4MZ available from Shikoku Fine Chemicals, Tokyo, Japan; “ERISYS” DDA or DDA accelerated with U-405, 24EMI, U-410 and U-415 available from CVC Specialty Chemicals, Maple Shade, N.J.; “AMICURE” PACM, 352, CG, CG-325 and CG-1200 available from Air Products, Allentown, Pa. Suitable fillers include fumed silica such as “CAB-O-SIL” L-90, LM-130, LM-5, PTG, M-5, MS-7, MS-55, TS-720, HS-5, EH-5 available from Cabot Corporation, Tuscola, Ill.; “AEROSIL” R972, R974, R805, R812, R812 S, R202, US204 and US206 available from Degussa, Akron, Ohio. Suitable clay fillers include BUCA, CATALPO, ASP NC, SATINTONE 5, SATINTONE SP-33, TRANSLINK 37, TRANSLINK 77, TRANSLINK 445, TRANSLINK 555 available from Engelhard Corporation, Edison, N.J. Suitable silica fillers are SILCRON G-130, G-300, G-100-T and G-100 available from SCM Chemicals, Baltimore, Md. Suitable silane coupling agents to improve the seal&#39;s hydrolytic stability are Z-6020, Z-6030, Z-6032, Z-6040, Z-6075 and Z-6076 available from Dow Corning Corporation, Midland, Mich. Suitable precision glass microbead spacers are available in an assortment of sizes from Duke Scientific, Palo Alto, Calif.  
         [0032]    The layer of a transparent electrically conductive material  128  is deposited on the second surface  112   b  to act as an electrode. Transparent conductive material  128  may be any material which bonds well to front element  112 , is resistant to corrosion to any materials within the electrochromic device, resistant to corrosion by the atmosphere, has minimal diffuse or specular reflectance, high light transmission, near neutral coloration and good electrical conductance. Transparent conductive material  128  may be fluorine doped tin oxide, tin doped indium oxide (ITO), ITO/metal/ITO (IMI) as disclosed in “Transparent Conductive Multilayer-Systems for FPD Applications”, by J. Stollenwerk, B. Ocker, K. H. Kretschmer of LEYBOLD AG, Alzenau, Germany, and the materials described in above-referenced U.S. Pat. No. 5,202,787, such as TEC 20 or TEC 15, available from Libbey Owens-Ford Co. of Toledo, Ohio. Generally, the conductance of transparent conductive material  128  will depend on its thickness and composition. IMI generally has superior conductivity compared with the other materials. IMI, however, is more difficult and expensive to manufacture and may be useful when high conductance is necessary. The thickness of the various layers in the IMI structure may vary but generally the thickness of the first ITO layer ranges from about 10 Å to about 200 Å, the metal ranges from about 10 Å to about 200 Å, and the second layer of ITO ranges from about 10 Å to about 200 Å. If desired, an optional layer or layers of a color suppression material  130  may be deposited between transparent conductive material  128  and the second surface  112   b  to suppress the reflection of any unwanted portions of the electromagnetic spectrum.  
         [0033]    In accordance with the present invention, a combination reflector/electrode  120  is disposed on third surface  114   a . Reflector/electrode  120  comprises at least one layer of a highly reflective material  121  which serves as a mirror reflectance layer and also forms an integral electrode in contact with and in a chemically and electrochemically stable relationship with any constituents in an electrochromic medium. As stated above, the conventional method of building electrochromic devices was to incorporate a transparent conductive material on the third surface as an electrode, and place a reflector on the fourth surface. By combining the “reflector” and “electrode,” and placing both on the third surface, several unexpected advantages arise, which not only make the device manufacture less complex, but also allow the device to operate with higher performance. The following will outline the exemplary advantages of the combined reflector/electrode of the present invention.  
         [0034]    First, the combined reflector/electrode  120  on the third surface generally has a higher conductance than a conventional transparent electrode and previously used reflector/electrodes which will allow greater design flexibility. One can change the composition of the transparent conductive electrode on the second surface to one that has lower conductance (being cheaper and easier to produce and manufacture) while maintaining coloration speeds similar to that obtainable with a fourth surface reflector device, while at the same time decreasing substantially the overall cost and time to produce the electrochromic device. If, however, performance of a particular design is of utmost importance, a moderate to high conductance transparent electrode can be used on the second surface, such as, for example, ITO, IMI, etc. The combination of a high conductance reflector/electrode on the third surface and a high conductance transparent electrode on the second surface will not only produce an electrochromic device with more even overall coloration, but will also allow for increased speed of coloration and clearing. Furthermore, in fourth surface reflector mirror assemblies there are two transparent electrodes with relatively low conductance and in previously used third surface reflector mirrors there is a transparent electrode and a reflector/electrode with relatively low conductance and, as such, a long buss bar on the front and rear element to bring current in and out is necessary to ensure adequate coloring speed. The third surface reflector/electrode of the present invention has a higher conductance and therefore has a very even voltage or potential distribution across the conductive surface, even with a small or irregular contact area. Thus, the present invention provides greater design flexibility by allowing the electrical contact for the third surface electrode to be very small while still maintaining adequate coloring speed.  
         [0035]    Second, a third surface reflector/electrode helps improve the image being viewed through the mirror. FIG. 1 shows how light travels through a conventional fourth surface reflector device. In the fourth surface reflector the light travels through: the first glass element; the transparent conductive electrode on the second surface; the electrochromic media; the transparent conductive electrode on the third surface; and the second glass element, before being reflected by the fourth surface reflector. Both transparent conductive electrodes exhibit highly specular transmittance but also possess diffuse transmittance and reflective components, whereas the reflective layer utilized in any electrochromic mirror is chosen primarily for its specular reflectance. By diffuse reflectance or transmittance component we mean a material which reflects or transmits a portion of any light impinging on it according to Lambert&#39;s law whereby the light rays are spread about or scattered. By specular reflectance or transmittance component we mean a material which reflects or transmits light impinging on it according to Snell&#39;s laws of reflection or refraction. In practical terms, diffuse reflectors and transmitters tend to slightly blur images, whereas specular reflectors show a crisp, clear image. Therefore, light traveling through a mirror having a device with a fourth surface reflector has two partial diffuse reflectors (on the second and third surface) which tend to blur the image, and a device with a third surface reflector/electrode of the present invention only has one diffuse reflector (on the second surface).  
         [0036]    Additionally, because the transparent electrodes act as partial diffuse transmitters, and the farther away the diffuse transmitter is from the reflecting surface the more severe the blurring becomes, a mirror with a fourth surface reflector appears significantly more hazy than a mirror with a third surface reflector. For example, in the fourth surface reflector shown in FIG. 1, the diffuse transmitter on the second surface is separated from the reflector by the electrochromic material, the second conductive electrode, and the second glass element. The diffuse transmitter on the third surface is separated from the reflector by the second glass element. By incorporating a combined reflector/electrode on the third surface in accordance with the present invention, one of the diffuse transmitters is removed and the distance between the reflector and the remaining diffuse transmitter is closer by the thickness of the rear glass element. Therefore, the third surface metal reflector/electrode of the present invention provides an electrochromic mirror with a superior viewing image.  
         [0037]    Finally, a third surface metal reflector/electrode improves the ability to reduce double imaging in an electrochromic mirror. As stated above, there are several interfaces where reflections can occur. Some of these reflections can be significantly reduced with color suppression or anti-reflective coatings; however, the most significant “double imaging” reflections are caused by misalignment of the first surface and the surface containing the reflector, and the most reproducible way of minimizing the impact of this reflection is by ensuring both glass elements are parallel. Presently, convex glass is often used for the passenger side and aspheric glass is sometimes used for the driver side mirror to increase the field of view and reduce potential blind spots. However, it is difficult to reproducibly bend successive elements of glass having identical radii of curvature. Therefore, when building an electrochromic mirror, the front glass element and the rear glass element may not be perfectly parallel (do not have identical radii of curvature) and, therefore, the otherwise controlled double imaging problems become much more pronounced. By incorporating a combined reflector electrode on the third surface of the device in accordance with the present invention, light does not have to travel through the rear glass element before being reflected, and any double imaging that occurs from the elements being out of parallel will be significantly reduced.  
         [0038]    It is desirable in the construction of outside rearview mirrors to incorporate thinner glass in order to decrease the overall weight of the mirror so that the mechanisms used to manipulate the orientation of the mirror are not overloaded. Decreasing the weight of the device also improves the dynamic stability of the mirror assembly when exposed to vibrations. Heretofore, no electrochromic mirrors incorporating a solution-phase electrochromic medium and two thin glass elements have been commercially available because thin glass suffers from being flexible and prone to warpage or breakage, especially when exposed to extreme environments. This problem is substantially improved by using an improved electrochromic device incorporating two thin glass elements having an improved gel material. This improved device is disclosed in commonly assigned U.S. Pat. No. 5,940,201 entitled “ELECTROCHROMIC MIRROR WITH TWO THIN GLASS ELEMENTS AND A GELLED ELECTROCHROMIC MEDIUM,” filed on Apr. 2, 1997. The entire disclosure of this U.S. Patent is hereby incorporated herein by reference. The addition of the combined reflector/electrode onto the third surface of the device further helps remove any residual double imaging resulting from the two glass elements being out of parallel.  
         [0039]    The most important factors for obtaining a reliable electrochromic mirror having a third surface reflector/electrode  120  are that the reflector/electrode has sufficient reflectance and that the mirror incorporating the reflector/electrode has adequate operational life. Regarding reflectance, the auto manufacturers require a highly reflective mirror for the inside mirror having a minimum reflectivity of at least 70 percent, whereas the reflectivity requirements for an outside mirrors are less stringent and generally must be at least 50 percent. To produce an electrochromic mirror with 70 percent, reflectance the reflector must have a higher reflectance because having the electrochromic medium in contact with the reflector will reduce the reflectance from that interface as compared to having the reflector in air due to the medium having a higher index of refraction as compared to air. Also, the glass, the transparent electrode, and the electrochromic medium even in its clear state are slightly light absorbing. Typically, if an overall reflectance of 70 percent is desired, the reflector must have a reflectance of about 80 percent. Therefore, highly reflectance in the context of the present invention means a reflector whose reflectance in air is at least 80 percent.  
         [0040]    Regarding operational life, the layer or layers that comprise the reflector/electrode  120  must have adequate bond strength to the peripheral seal, the outermost layer must have good shelf life between the time it is coated and the time the mirror is assembled, the layer or layers must be resistant to atmospheric and electrical contact corrosion, and must bond well to the glass surface or to other layers disposed beneath it, e.g., the base or intermediate layer ( 122  or  123 , respectively). The overall sheet resistance for the reflector/electrode  120  may range from about 0.01 Ω/□ to about 20 Ω/□ and preferably ranges from about 0.2 Ω/□ to about 6 Ω/□. As will be discussed in more detail below, improved electrical interconnections using a portion of the third surface reflector/electrode as a high conductance contact or buss bar for the second surface transparent conductive electrode may be utilized when the conductance of the third surface reflector/electrode is below about 2 Ω/□.  
         [0041]    Referring to FIG. 3 for one embodiment of the present invention, a reflector/electrodes that is made from a single layer of a highly reflective silver alloy  121  is provided that is in contact with at least one solution-phase electrochromic material. The layer of silver alloy covers the entire third surface  114   a  of second element  114 , provided that a section of the reflector/electrode may be removed for a display device and a glare sensor, in accordance with U.S. Pat. No. 5,825,527 entitled “INFORMATION DISPLAY AREA ON ELECTROCHROMIC MIRRORS HAVING A THIRD SURFACE REFLECTOR” and filed on Apr. 2, 1997. This application is hereby incorporated in its entirety herein by reference. The highly reflective silver alloy means a homogeneous or non-homogeneous mixture of silver and one or more metals, or an unsaturated, saturated, or supersaturated solid solution of silver and one or more metals. The thickness of highly reflective layer  121  ranges from about 50 Å to about 2000 Å and more preferably from about 200 Å to about 1000 Å. If highly reflective layer  121  is disposed directly to the glass surface, it is preferred that the glass surface be treated by plasma discharge to improve adhesion.  
         [0042]    Table 1 shows the relevant properties for a number of different metals that have been proposed for third surface reflectors as compared with the materials suitable for the reflector/electrode  120  of the present invention. The only materials in Table 1 having reflectance properties suitable for use as a third surface reflector/electrode in contact with at least one solution-phase electrochromic material for an inside electrochromic mirror for a motor vehicle are aluminum, silver, and silver alloys. Aluminum performs very poorly when in contact with solution-phase material(s) in the electrochromic medium because aluminum reacts with or is corroded by these materials. The reacted or corroded aluminum is non-reflective and non-conductive and will typically dissolve off, flake off, or delaminate from the glass surface. Silver is more stable than aluminum but can fail when deposited over the entire third surface because it does not have long shelf life and is not resistant to electrical contact corrosion when exposed to the environmental extremes found in the motor vehicle environment. These environmental extremes include temperatures ranging from about −40° C. to about 85° C., and humidities ranging from about 0 percent to about 100 percent. Further, mirrors must survive at these temperatures and humidities for coloration cycle lives up to 100,000 cycles. The other prior art materials (silver/copper, chromium, stainless steel, rhodium, platinum, palladium, Inconel®, copper or titanium) suffer from any one of a number of deficiencies such as: very poor color neutrality (silver/copper and copper); poor reflectance (chromium, stainless steel, rhodium, platinum, palladium, Inconel®, and titanium); or poor cleanability (chromium).  
         [0043]    When silver is alloyed with certain materials to produce a third surface reflector/electrode, the deficiencies associated with silver metal and aluminum metal can be overcome. Suitable materials for the reflective layer are alloys of silver/palladium, silver/gold, silver/platinum, silver/rhodium, silver/titanium, etc. The amount of the solute material, i.e., palladium, gold, etc., can vary. As can be seen from Table 1, the silver alloys surprisingly retain the high reflectance and low sheet resistance properties of silver, while simultaneously improving their contact stability, shelf life, and also increasing their window of potential stability when used as electrodes in propylene carbonate containing 0.2 molar tetraethylammonium tetrafluoroborate. The presently preferred materials for highly reflective layer  121  are Ag/Au, Ag/Pt and Ag/Pd.  
         [0044]    More typically, reflector/electrode  120  has, in addition to the layer of a highly reflective alloy  121 , an optional base layer of a conductive metal or alloy  122  deposited directly on the third surface  114   a . There may also be an optional intermediate layer of a conductive metal or alloy  123  disposed between the layer of highly reflective material  121  and the base coat  122 . If reflector/electrode  120  includes more than one layer, there should not be galvanic corrosion between the two metals or alloys. If optional base layer  122  is deposited between the highly reflective layer  121  and the glass element  114 , it should be environmentally rugged, e.g., bond well to the third (glass) surface  114   a  and to highly reflective layer  121 , and maintain this bond when the seal  116  is bonded to the reflective layer. Base layer  122  should have a thickness from about 50 Å to about 2000 Å and more preferably from about 100 Å to about 1000 Å. Suitable materials for the base layer  122  are chromium, stainless steel, titanium, and alloys of chromium/molybdenum/nickel, molybdenum and nickel-based alloys (commonly referred to as Inconel®, available from Castle Metals, Chicago, Ill.). The main constituents of Inconel® are nickel which may range from 52 percent to 76 percent (Inconel® 617 and 600, respectfully), iron which may range from 1.5 percent to 18.5 percent (Inconel® 617 and Inconel® 718, respectfully) and chromium which may range from 15 percent to 23 percent (Inconel® 600 and Inconel® 601, respectfully). Inconel® 617 having 52 percent nickel, 1.5 percent iron, 22 percent chromium, and typical “other” constituents including 12.5 percent cobalt, 9.0 percent molybdenum and 1.2 percent aluminum was used in the present examples.  
         [0045]    In some instances it is desirable to provide an optional intermediate layer  123  between the highly reflective layer  121  and the base layer  122  in case the material of layer  121  does not adhere well to the material of layer  122  or there are any adverse interactions between the materials, e.g., galvanic corrosion. If used, intermediate layer  123  should exhibit environmental ruggedness, e.g., bond well to the base layer  122  and to the highly reflective layer  121 , and maintain this bond when the seal member  116  is bonded to the highly reflective layer  121 . The thickness of intermediate layer  123  ranges from about 50 Å to about 2000 Å and more preferably from about 100 Å to about 1000 Å. Suitable materials for the optional intermediate layer  123  are molybdenum, rhodium, stainless steel, titanium, copper, nickel, and platinum. Reference is made to examples 1 and 2 to show how the insertion of a rhodium intermediate layer between a chromium base layer and a silver or silver alloy reflective layer increases the time to failure in copper-accelerated acetic acid-salt spray (CASS) by a factor of 10. Example 4 shows how the insertion of a molybdenum intermediate layer between a chromium base layer and a silver alloy having a molybdenum flash over-coat layer increases the time to failure in CASS by a factor of 12.  
         [0046]    Finally, it is sometimes desirable to provide an optional flash over-coat  124  over highly reflective layer  121  such that it (and not the highly reflective layer  121 ) contacts the electrochromic medium. This flash over-coat layer  124  must have stable behavior as an electrode, it must have good shelf life, it must bond well to the highly reflective layer  121  and maintain this bond when the seal member  116  is bonded thereto. It must be sufficiently thin such that it does not completely block the reflectivity of highly reflective layer  121 . In accordance with another embodiment of the present invention, when a very thin flash over-coat  124  is placed over the highly reflective layer, then the highly reflective layer  121  may be silver metal or a silver alloy because the flash layer protects the highly reflective layer while still allowing the highly reflective layer  121  to contribute to the reflectivity of the mirror. In such cases, a thin (between about 25 Å and about 300 Å) layer of rhodium, platinum or molybdenum is deposited over the highly reflective layer  121 .  
         [0047]    It is preferred but not essential that the third surface reflector/electrode  120  be maintained as the cathode in the circuitry because this eliminates the possibility of anodic dissolution or anodic corrosion that might occur if the reflector/electrode was used as the anode. Although as can be seen in Table 1, if certain silver alloys are used the positive potential limit of stability extends out far enough, e.g., 1.2 V, that the silver alloy reflector/electrode could safely be used as the anode in contact with at least one solution-phase electrochromic material.  
                                                             TABLE 1                           White Light   Reflectance       Negative Potential Limit   Positive Potential Limit           Reflectance   In Device   Contact   of Window of Potential   Window of Potential       Metal   In Air   (%)   Stability   Stability (V)   Stability (V)                                Al   &gt;92   N/A   very poor   N/A   N/A       Cr   65   N/A   poor   N/A   N/A       Stainless   60   N/A   good   N/A   N/A       Steel       Rh   75   N/A   very good   N/A   N/A       Pt   72   N/A   very good   N/A   N/A       Inconel   55   N/A   N/A   N/A   N/A       Ag   97   84   fair   −2.29   0.86       Ag2.7Pd   93   81   good   −2.26   0.87       Ag10Pd   80   68   good   −2.05   0.97       Ag6Pt   92   80   good   −1.66*   0.91       Ag6Au   96   84   good   −2.25   0.98       Ag15Au   94   82   good   −2.3   1.2                          
 
         [0048]    The various layers of reflector/electrode  120  can be deposited by a variety of deposition procedures, such as RF and DC sputtering, e-beam evaporation, chemical vapor deposition, electrodeposition, etc., that will be known to those skilled in the art. The preferred alloys are preferably deposited by sputtering (RF or DC) a target of the desired alloy or by sputtering separate targets of the individual metals that make up the desired alloy such that the metals mix during the deposition process and the desired alloy is produced when the mixed metals deposit and solidify on the substrate surface.  
         [0049]    In another embodiment, the reflector/electrode  120 , shown in FIG. 4, has at least two layers ( 121  and  122 ) where at least one layer of a base material  122  covers the entire portion of the third surface  114   a  (except for sections removed for a display device and a glare sensor in accordance with the U.S. Pat. No. 5,825,527 entitled “INFORMATION DISPLAY AREA ON ELECTROCHROMIC MIRRORS HAVING A THIRD SURFACE REFLECTOR”) and at least one layer of a highly reflective material  121  covers the inner section of the third surface  114   a  but does not cover the peripheral edge portion  125  where seal member  116  is disposed. Peripheral portion  125  may be created by masking that portion of layer  122  during deposition of the layer of highly reflective material  121 , or the layer of highly reflective material may be deposited over the entire third surface and subsequently removed or partially removed in the peripheral portion. The masking of layer  122  may be accomplished by use of a physical mask or through other well-known techniques such as photolithography and the like. Alternatively, layer  121  may be partially removed in the peripheral portion by a variety of techniques, such as, for example, by etching (laser, chemical or otherwise), mechanical scraping, sandblasting or otherwise. Laser etching is the presently preferred method because of its accuracy, speed and control. Partial removal is preferably accomplished by laser etching in a pattern where enough metal is removed to allow the seal member  116  to bond directly to the third surface  114   a  while leaving enough metal in this area such that the conductance in this area is not significantly reduced. For example, the metal may be removed in a dot pattern or other pattern as taught for removal of metal for information display in the immediately above-referenced U.S. Pat. No. 5,827,527.  
         [0050]    In addition, an optional intermediate layer of a conductive material  123  may be placed over the entire area of third surface  114   a  and disposed between the highly reflective layer  121  and the base layer  122 , or it may be placed only under the area covered by layer  121 , i.e., not in peripheral edge portion  125 . If this optional intermediate layer is utilized, it can cover the entire area of third surface  114   a  or it may be masked or removed from peripheral edge portion  125  as discussed above.  
         [0051]    An optional flash over-coat layer  124  may be coated over the highly reflective layer  121 . The highly reflective layer  121 , the optional intermediate layer  123 , and the base layer  122  preferably have properties similar to that described above, except that the layer of highly reflective material  121  need not bond well to the epoxy seal since it is removed in the peripheral portion where seal member is  116  placed. Because the interaction with the epoxy seal is removed, silver metal itself, in addition to the alloys of silver described above, will function as the highly reflective layer.  
         [0052]    Referring again to FIG. 3, chamber  125 , defined by transparent conductor  128  (disposed on front element rear surface  112   b ), reflector/electrode  120  (disposed on rear element front surface  114   a ), and an inner circumferential wall  132  of sealing member  116 , contains an electrochromic medium  126 . Electrochromic medium  126  is capable of attenuating light traveling therethrough and has at least one solution-phase electrochromic material in intimate contact with reflector/electrode  120  and at least one additional electroactive material that may be solution-phase, surface-confined, or one that plates out onto a surface. However, the presently preferred media are solution-phase redox electrochromics, such as those disclosed in above-referenced U.S. Pat. Nos. 4,902,108, 5,128,799, 5,278,693, 5,280,380, 5,282,077, 5,294,376, and 5,336,448. Co-filed U.S. Pat. No. 6,020,987 entitled “AN IMPROVED ELECTROCHROMIC MEDIUM CAPABLE OF PRODUCING A PRE-SELECTED COLOR” discloses electrochromic media that are perceived to be gray throughout their normal range of operation. The entire disclosure of this application is hereby incorporated herein by reference. If a solution-phase electrochromic medium is utilized, it may be inserted into chamber  125  through a sealable fill port  142  through well-known techniques, such as vacuum backfilling and the like.  
         [0053]    A resistive heater  138 , disposed on the fourth glass surface  114   b , may optionally be a layer of ITO, fluorine-doped tin oxide, or may be other heater layers or structures well known in the art. Electrically conductive spring clips  134   a  and  134   b  are placed on the coated glass sheets ( 112  and  114 ) to make electrical contact with the exposed areas of the transparent conductive coating  128  (clip  134   b ) and the third surface reflector/electrode  120  (clip  134   a ). Suitable electrical conductors (not shown) may be soldered or otherwise connected to the spring clips ( 134   a  and  134   b ) so that a desired voltage may be applied to the device from a suitable power source.  
         [0054]    An electrical circuit  150 , such as those taught in the above-referenced Canadian Patent No. 1,300,945 and U.S. Pat. Nos. 5,204,778, 5,434,407, and 5,451,822, is connected to, and allows control of the potential to be applied across, reflector/electrode  120  and transparent electrode  128  such that electrochromic medium  126  will darken and thereby attenuate various amounts of light traveling therethrough and thus vary the reflectance of the mirror containing electrochromic medium  126 .  
         [0055]    As stated above, the low resistance of reflector/electrode  120  allows greater design flexibility by allowing the electrical contact for the third surface reflector/electrode to be small while maintaining adequate coloring speed. This flexibility extends to improving the interconnection techniques to the layer of transparent conductive material  128  on the second surface  112   b . Referring now to FIGS. 5 a  and  5   b , an improved mechanism for applying a drive potential to the layer of transparent conductive material  128  is shown. Electrical connection between the power supply and the layer of transparent conductive material  128  is made by connecting the buss bars (or clips  119   a ) to the area of reflector/electrode  120   a  such that the drive potential travels through the area of reflector/electrode  120   a  and the conductive particles  116   b  in sealing member  116  before reaching the transparent conductor  128 . Reflector/electrode must not be present in area  120   c  so that there is no chance of current flow from reflector/electrode area  120   a  to  120   b . This configuration is advantageous in that it allows connection to the transparent conductive material  128  nearly all the way around the circumference and therefore improves the speed of dimming and clearing of the electrochromic media  126 .  
         [0056]    In such a configuration, sealing member  116  comprises a typical sealing material, e.g., epoxy  116   a , with conductive particles  116   b  contained therein. The conductive particles may be small, such as, for example, gold, silver, copper, etc., coated plastic with a diameter ranging from about 5 microns to about 80 microns, in which case there must be a sufficient number of particles to ensure sufficient conductivity between the reflector/electrode area  120   a  and the transparent conductive material  128 . Alternatively, the conductive particles may be large enough to act as spacers, such as, for example, gold, silver, copper, etc., coated glass or plastic beads. The reflector/electrode  120  is separated into two distinct reflector/electrode areas ( 120   a  and  120   b , separated by an area  120   c  devoid of reflector/electrode). There are many methods of removing the reflector/electrode  120  from area  120   c , such as, for example, chemical etching, laser ablating, physical removal by scraping, etc. Deposition in area  120   c  can also be avoided by use of a mask during deposition of reflector/electrode. Sealing member  116  with particles  116   b  contacts area  120   a  such that there is a conductive path between reflector/electrode area  120   a  and the layer of transparent conductive material  128 . Thus, electrical connection to the reflector/electrode area  120   b  that imparts a potential to the electrochromic medium is connected through clips  119   b  to the electronic circuitry at reflector/electrode area  120   d  (FIG. 5 b ). No conductive particles  116   b  can be placed in this reflector/electrode area  120   b  because of the possibility of an electrical short between reflector/electrode area  120   b  and the layer of transparent conductive material  128 . If such an electrical short occurred, the electrochromic device would not operate properly. Additionally, no conductive seal  116   b  should be present in area  120   d.    
         [0057]    A variety of methods can be used to ensure that no conductive particles  116   b  enter into this reflector/electrode area  120   b , such as, for example, disposing a nonconductive material into the area  120   c  of reflector/electrode devoid of conductive material. A dual dispenser could be used to deposit the seal  116  with conductive particles  116   b  onto reflector/electrode area  120   a  and simultaneously deposit the nonconductive material into reflector/electrode area  120   c . Another method would be to cure a nonconductive seal in area  120   c  and then dispose a conductive material  116   c  into the edge gap to electrically interconnect reflector/electrode area  120   a  with transparent conductive layer  128 . A general method of ensuring that no conductive particles reach reflector/electrode area  120   b  is to make sure seal  116  has proper flow characteristics such that the conductive portion  116   b  tents to stay behind as the sealant is squeezed out during assembly and only the non-conductive portion of  116  flows into area  120   b . In an alternative embodiment, spacer member  116  need not contain conductive particles and a conductive member or material  116   c  may be placed on or in the outer edge of member  116  to interconnect transparent conductive material  128  to reflector/electrode area  120   a.    
         [0058]    Yet another embodiment of an improved electrical interconnection technique is illustrated in FIG. 6 where a first portion of seal member  116  is applied directly onto the third surface  114   a  and cured prior to the application of reflector/electrode  120 . After the reflector/electrode  120  is deposited onto the third surface  114   a  over the first portion of seal member  116 , a portion of the cured seal member  116  is machined off to leave  116   i  as shown with a predetermined thickness (which will vary depending on the desired cell spacing between the second surface  112   b  and the third surface  114   a ). The cell spacing ranges from about 20 microns to about 400 microns, and preferably range from about 90 microns to about 230 microns. By curing the first portion of seal member and machining it to a predetermined thickness ( 116   i ), the need for glass beads to ensure a constant cell spacing is eliminated. Glass beads are useful to provide cell spacing, however, they provide stress points where they contact reflector/electrode  120  and transparent conductor  128 . By removing the glass beads these stress points are also removed. During the machining, the reflector/electrode  120  that is coated on the first portion of seal member  116  is removed to leave an area devoid of reflector/electrode  120 . A second portion of seal member  116   ii  is then deposited onto the machined area of the first portion of seal member  116   i  or on the coatings on second surface  112   b  in the area corresponding to  116   i , and seal member  116   ii  is cured after assembly in a conventional manner. Finally, an outer conductive seal member  117  may optionally be deposited on the outer peripheral portion of seal member  116  to make electrical contact between the outer edge of reflector/electrode  120  and the outer peripheral edge of the layer of transparent conductive material  128 . This configuration is advantageous in that it allows connection to the transparent conductive material  128  nearly all the way around the circumference and therefore improves the speed of dimming and clearing of the electrochromic media  126 .  
         [0059]    Referring again to FIG. 2, rearview mirrors embodying the present invention preferably include a bezel  144 , which extends around the entire periphery of each individual assembly  110 ,  111   a , and/or  111   b . The bezel  144  conceals and protects the spring clips  134   a  and  134   b  of FIG. 3, (or  116   a  and  116   b  of FIG. 5 a ,  116   i ,  116   ii  and  117  of FIG. 6) and the peripheral edge portions of sealing member and both the front and rear glass elements ( 112  and  114 , respectively). A wide variety of bezel designs are well known in the art, such as, for example, the bezel taught and claimed in above-referenced U.S. Pat. No. 5,448,397. There are also a wide variety of housing well known in the art for attaching the mirror assembly  110  to the inside front windshield of an automobile, or for attaching the mirror assemblies  111   a  and  111   b  to the outside of an automobile. A preferred mounting bracket is disclosed in above-referenced U.S. Pat. No. 5,337,948.  
         [0060]    The electrical circuit preferably incorporates an ambient light sensor (not shown) and a glare light sensor  160 , the glare light sensor being positioned either behind the mirror glass and looking through a section of the mirror with the reflective material completely or partially removed, or the glare light sensor can be positioned outside the reflective surfaces, e.g., in the bezel  144 . Additionally, an area or areas of the electrode and reflector, such as  146 , may be completely removed, or partially removed in, for example, a dot or line pattern, to permit a vacuum fluorescent display, such as a compass, clock, or other indicia to show through to the driver of the vehicle. Above-referenced U.S. Pat. No. 5,825,527 entitled “INFORMATION DISPLAY AREA ON ELECTROCHROMIC MIRRORS HAVING A THIRD SURFACE REFLECTOR” shows a presently preferred line pattern. The present invention is also applicable to a mirror which uses only one video chip light sensor to measure both glare and ambient light and which is further capable of determining the direction of glare. An automatic mirror on the inside of a vehicle, constructed according to this invention, can also control one or both outside mirrors as slaves in an automatic mirror system  
         [0061]    The following illustrative examples are not intended to limit the scope of the present invention but to illustrate its application and use:  
       EXAMPLE 1  
       [0062]    Electrochromic mirror devices incorporating a high reflectivity third surface reflector/electrode were prepared by sequentially depositing approximately 700 angstroms of chromium and approximately 500 angstroms of silver on the surface of 2.3 millimeter thick sheets of flat soda lime float glass cut to an automotive mirror element shape. A second set of high reflectivity third surface reflector/electrodes were also prepared by sequentially depositing 700 angstroms of chromium and approximately 500 angstroms of a silver alloy containing 3 percent by weight palladium on the glass element shapes. The deposition was accomplished by passing the said glass element shapes past separate metal targets in a magnetron sputtering system with a base pressure of 3×10 −6  torr and an argon pressure of 3×10 −3  torr.  
         [0063]    The chromium/silver and chromium/silver 3 percent palladium alloy coated glass automotive mirror shapes were used as the rear planar elements of an electrochromic mirror device. The front element was a sheet of TEC 15 transparent conductor coated glass from LOF cut similar in shape and size to the rear glass element. The front and rear elements were bonded together by an epoxy perimeter seal with the conductive planar surfaces facing each other and parallel to each other with an offset. The spacing between the electrodes was about 137 microns. The devices were vacuum filled through a fill port left in the perimeter seal with an electrochromic solution made up of:  
         [0064]    0.028 molar 5,10-dihydro-5-10-dimethylphenazine  
         [0065]    0.034 molar 1,1′-di(3-phenyl(n-propane))-4,4′-bipyridinium di(tetrafluoroborate)  
         [0066]    0.030 molar 2-(2′-hydroxy-5′-methylphenyl)-benzotriazole  
         [0067]    in a solution of 3 weight percent Elvacite™ 2051 polymethylmethacrylate resin dissolved in propylene carbonate.  
         [0068]    The fill port was plugged with a UV cure adhesive which was cured by exposure to UV light.  
         [0069]    The devices were subjected to accelerated durability tests until the seal integrity of the device was breached or the lamination of the reflector/electrode layers or the transparent electrode layers was substantially degraded or dilapidated at which time the said device is said to fail. The first test performed was steam autoclave testing in which the devices were sealed in a water-containing vessel and subjected to 120° C. at a pressure of 15 pounds per square inch (psi). The second test performed was copper-accelerated acetic acid-salt spray (CASS) as described in ASTM B 368-85.  
         [0070]    When the electrochroric devices were observed after one day in testing, all of the devices failed to withstand the CASS testing and all of the devices failed to withstand the steam autoclave testing.  
       EXAMPLE 2  
       [0071]    Other than as specifically mentioned, the devices in this example were constructed in accordance with the conditions and teachings in Example 1. Multilayer combination reflector/electrodes were prepared by sequentially depositing approximately 700 angstroms chromium, approximately 100 angstroms rhodium, and approximately 500 angstroms of silver on the surface of said glass element shapes. A second set of multilayer combination reflector/electrodes were also prepared by sequentially depositing approximately 700 angstroms of chromium, approximately 100 angstroms rhodium, and approximately 500 angstroms of a silver alloy containing 3 percent by weight palladium on the surface of said glass element shapes. The electrochromic devices were constructed and tested in accordance with Example 1.  
         [0072]    The device incorporating the sequential multilayer combination reflector electrode of chromium, rhodium, and silver withstood steam autoclave testing two times longer and CASS testing 10 times longer than the device in Example 1 before failure occurred. The device incorporating the sequential multilayer combination reflector electrode of chromium, rhodium, and silver 3 percent palladium alloy withstood steam autoclave testing three times longer and CASS testing 10 times longer than devices in Example 1 before failure occurred.  
       EXAMPLE 3  
       [0073]    Other than as specifically mentioned, the devices in this example were constructed in accordance with the conditions and teachings in Example 1. Multilayer combination reflector/electrodes were prepared by sequentially depositing approximately 700 angstroms chromium, approximately 500 angstroms molybdenum, and approximately 500 angstroms of a silver alloy containing 3 percent by weight palladium on the surface of said glass element shapes. The electrochromic devices were constructed and tested in accordance with Example 1.  
         [0074]    The device incorporating the sequential multilayer combination reflector electrode of chromium, molybdenum, and silver 3 percent palladium alloy withstood CASS testing 10 times longer than devices in Example 1 before failure occurred.  
       EXAMPLE 4  
       [0075]    Other than as specifically mentioned, the devices in this example were constructed in accordance with the conditions and teachings in Example 1. Multilayer combination reflector/electrodes were prepared by sequentially depositing approximately 700 angstroms chromium, approximately 500 angstroms of a silver alloy containing 3 percent by weight palladium, and approximately 100 angstroms of molybdenum on the surface of said glass element shapes. A second set of multilayer combination reflector/electrodes were also prepared by sequentially depositing approximately 700 angstroms of chromium, approximately 500 angstroms molybdenum, approximately 500 angstroms of a silver alloy containing 3 percent by weight palladium, and approximately 100 angstroms of molybdenum on the surface of said glass element shapes. The electrochromic devices were constructed and tested in accordance with Example 1.  
         [0076]    The device incorporating the sequential multilayer combination reflector electrode of chromium, molybdenum, silver 3 percent palladium, molybdenum withstood steam autoclave testing 25 percent longer and CASS testing twelve times longer than the sequential multilayer combination reflector electrode device of chromium, silver 3 percent palladium, molybdenum before failure occurred. Also, the device incorporating the sequential multilayer combination reflector electrode of chromium, molybdenum, silver 3 percent palladium, molybdenum withstood CASS testing three times longer than the device constructed in Example 3. Finally, the sequential multilayer combination reflector electrode device of chromium, silver 3 percent palladium, molybdenum withstood two times longer in CASS testing and twenty times longer in steam autoclave testing than the sequential multilayer combination reflector electrode device of chromium, silver 3 percent palladium of Example 1.  
       EXAMPLE 5  
       [0077]    Other than as specifically mentioned, the devices in this example were constructed in accordance with the conditions and teachings in Example 1. Multilayer combination reflector/electrodes were prepared by sequentially depositing approximately 700 angstroms chromium, approximately 100 angstroms rhodium, and approximately 500 angstroms of silver on the surface of said glass element shapes. A second set of multilayer combination reflector/electrodes were also prepared by sequentially depositing approximately 700 angstroms of chromium, approximately 100 angstroms rhodium and approximately 500 angstroms of a silver alloy containing 3 percent by weight palladium on the surface of said glass element shapes. A third set of multilayer combination reflector/electrodes were also prepared by sequentially depositing approximately 700 angstroms of chromium, approximately 100 angstroms rhodium and approximately 500 angstroms of a silver alloy containing 6 percent by weight platinum on the surface of said glass element shapes. A fourth set of multilayer combination reflector/electrodes were also prepared by sequentially depositing approximately 700 angstroms of chromium, approximately 100 angstroms rhodium and approximately 500 angstroms of a silver alloy containing 6 percent by weight gold on the surface of said glass element shapes. A fifth set of multilayer combination reflector/electrodes were also prepared by sequentially depositing approximately 700 angstroms of chromium, approximately 100 angstroms rhodium and approximately 500 angstroms of a silver alloy containing 15 percent by weight gold on the surface of said glass element shapes. The electrochromic devices were constructed in accordance with Example 1.  
         [0078]    Conductive clips were connected to the offset portions of the front and rear elements of the devices. A power source was connected to the clips and 1.2 volts were applied to the devices continuously for approximately 250 hours at approximately 20° C., with the connection arranged such that the reflector/electrode was the cathode. The device incorporating the sequential multilayer combination reflector electrode of chromium, rhodium, and silver exhibited a yellowing effect within the electrochromic medium. This yellowing phenomenon was not apparent in any of the silver alloy devices.  
         [0079]    While the invention has been described in detail herein in accordance with certain preferred embodiments thereof, many modifications and changes therein may be effected by those skilled in the art without departing from the spirit of the invention. Accordingly, it is our intent to be limited only by the scope of the appending claims and not by way of the details and instrumentalities describing the embodiments shown herein.