Abstract:
An improved electro-optic rearview mirror for motor vehicles, the mirror incorporating an improved display, such as &#34;HEATED&#34; or &#34;OBJECTS IN MIRROR ARE CLOSER THAN THEY APPEAR&#34; or the like, and wherein the mirror colors and clears uniformly and the display is effected in an aesthetically pleasing manner.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/002,942, filed Aug. 30, 1995. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention relates to image/information displays on electro-optic devices and, more particularly, to improved image/information displays on electrochromic mirrors for motor vehicles. 
     Heretofore, various automatic rearview mirrors for motor vehicles have been devised which automatically change from the full reflectance mode (day) to the partial reflectance mode (night) for glare protection purposes from light emanating from the headlights of vehicles approaching from the rear. The electrochromic mirrors disclosed in U.S. Pat. No. 4,902,108, issued Feb. 20, 1990, for Single-Compartment, Self-Erasing, Solution-Phase Electrochromic Devices, Solutions for Use Therein, and Uses Thereof; U.S. Pat. No. 4,917,477, issued Apr. 17, 1990, for Automatic Rearview Mirror System for Automotive Vehicles; U.S. Pat. No. 5,128,799, issued Jul. 7, 1992, for Variable Reflectance Motor Vehicle Mirror; U.S. Pat. No. 5,202,787, issued Apr. 13, 1993, for Electro-Optic Device; U.S. Pat. No. 5,280,380, issued Jan. 18, 1994, for UV-Stabilized Compositions and Methods; and U.S. Pat. No. 5,282,077, issued Jan. 25, 1994, for Variable Reflectance Mirror, each of which patents is assigned to the assignee of the present invention and the disclosures of each of which are hereby incorporated herein by reference, are typical of modern day automatic rearview mirrors for motor vehicles. Such electrochromic mirrors may be utilized in a fully integrated inside/outside rearview mirror system or as an inside or an outside rearview mirror system. In general, in automatic rearview mirrors of the types disclosed in U.S. Pat. Nos. 4,902,108; 4,917,477; 5,128,799; 5,202,787, 5,280,380 and 5,282,077, both the inside and the outside rearview mirrors are comprised of a relatively thin electro-optic medium sandwiched and sealed between two glass elements. In most cases, when the electro-optic medium is electrically energized, it darkens and begins to absorb light, and the higher the voltage, the darker the mirror becomes. When the electrical voltage is decreased to zero, the mirror returns to its clear state. Also, in general, the electro-optic medium sandwiched and sealed between the two glass elements is preferably comprised of solutions of electrochromic compounds which function as the media of variable transmittance in the mirrors, although it should be understood that other electro-optic media may be utilized, including an approach wherein a tungsten oxide electrochromic layer is coated on one electrode with a solution containing at least another compound to provide counter electrode reaction. When operated automatically, the rearview mirrors of the indicated character generally incorporate light-sensing electronic circuitry which is effective to change the mirrors to the dimmed reflectance modes when glare is detected, the sandwiched electro-optic medium being activated and the mirror being dimmed in proportion to the mount of glare that is detected. As glare subsides, the mirror automatically returns to its normal high reflectance state without any action being required on the part of the driver of the vehicle. The electro-optic medium is disposed in a sealed chamber defined by a transparent front glass element, a peripheral edge seal, and a rear mirror element having a reflective layer, the electro-optic medium filling the chamber. Conductive layers are provided on the inside of the front and rear glass elements, the conductive layer on the front glass element being transparent while the conductive layer on the rear glass element may be transparent or the conductive layer on the rear glass element may be semi-transparent or opaque and also have reflective characteristics and function as the reflective layer for the mirror assembly. The conductive layers on both the front glass element and the rear glass element are connected to electronic circuitry which is effective to electrically energize the electro-optic medium to switch the mirror to nighttime, decreased reflectance modes when glare is detected and thereafter allow the mirror to return to the daytime, high reflectance mode when the glare subsides as described in detail in the aforementioned U.S. patents. For clarity of description of such a structure, the front surface of the front glass element is sometimes referred to hereinafter 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. 
     In the past, information or images or symbols, such as &#34;HEATED&#34; or &#34;OBJECTS IN MIRROR ARE CLOSER THAN THEY APPEAR&#34; or other indicative symbols have been displayed on rearview mirrors for motor vehicles, particularly on outside rearview mirrors. For example, with first surface chromium type reflective mirrors, such information has been sandblasted, etched or otherwise formed on the front reflective surface. With fourth surface reflector electrochromic mirrors, such information has been sandblasted, etched or otherwise formed on the fourth surface. However, these methods are not suitable for use with a third surface reflector because of double image parallax in the case of first surface imaging, or the image not being visible because it is behind the reflective surface in the case of the fourth surface imaging. Moreover, neither of these methods are aesthetically acceptable. 
     In accordance with the present invention, improved means is provided for displaying information or images or symbols, such as &#34;HEATED&#34; or &#34;OBJECTS IN MIRROR ARE CLOSER THAN THEY APPEAR&#34; or the like on electrochromic mirrors for automotive vehicles, particularly on outside rearview mirrors although it will be understood that, if desired, information or images may be displayed on inside electrochromic mirrors. 
     In accordance with one aspect of the present invention, a reflective layer is provided on the inside (third surface) of the back glass of an electrochromic rearview mirror, which layer may, for example, also form an integral electrode in contact with the electrochromic media, i.e. a combination reflector/electrode. The other electrode on the inside (second) surface of the front glass is a transparent electrode which also contacts the electrochromic media inside the mirror element. The reflector/electrode may be comprised, for example, of a base reflective coating which bonds to the glass surface, and a transparent conductive over coating which directly contacts the electrochromic media. It will be understood that the reflector/electrode may have one or more base coatings and one or more over coatings or a single layer may perform both the reflective and the conductive functions. 
     The transparent coating on the second surface of the mirror is preferably fluorine doped tin oxide, tin doped indium oxide (ITO) or a series of metal oxide coatings with base coatings to suppress color and reflection followed by an electrically conductive, transparent coating which contacts the electrochromic media directly. The materials are preferably chosen for good bonding, resistance to corrosion by the materials of the electrochromic media, resistance to corrosion by the atmosphere, minimal reflectance, high light transmission, neutral coloration and high electrical conductance. Also, to a considerable extent, it is possible to make the reflective electrode very high in electrical conductance to compensate in a synergistic fashion with a transparent electrode that is lower in electrical conductance so the net result is an electrochromic mirror which darkens and clears acceptably fast and uniformly with excellent optical properties. 
     This synergistic structure is applicable for both inside and outside rearview mirrors for motor vehicles. When the multilayer combination reflector/electrode is used in any mirror, it has the inherent advantage of reducing double images, distortion, and multiple images from raindrops, dust, etc., while providing excellent speed of reflectance change, good high end reflectance, good uniformity of reflectance change across the surface area of the mirror, neutral color, continually variable reflectance and a low end reflectance low enough to relieve strong glare. The reduction in double images and distortion is particularly useful in the case of dimmable convex mirrors which use glass that is bent but may have slight variations in radius of curvature or slight ripple or warp that result in slight imperfections in matching two pieces of bent glass required to make a convex, solution based electrochromic mirror. 
     An object of the present invention is to overcome disadvantages in prior rearview mirrors of the indicated character and to provide an improved electrochromic rearview mirror for motor vehicles, which mirror incorporates improved means for displaying information or images or symbols, such as &#34;HEATED&#34; or &#34;OBJECTS IN MIRROR ARE CLOSER THAN THEY APPEAR&#34; or the like, on the mirror. 
     Another object of the present invention is to provide an improved electrochromic rearview mirror which colors and clears uniformly and which displays information or images or symbols on the mirror in an aesthetically pleasing manner. 
     Another object of the present invention is to provide an improved electrochromic rearview mirror for motor vehicles, which mirror incorporates improved means for economically and efficiently displaying information or images or symbols on the mirror in a reliable manner. 
     Still another object of the present invention is to provide an improved electrochromic rearview mirror for motor vehicles wherein excellent speed of reflective change, good high end reflectance, good uniformity of reflectance change across the surface area of the mirror, neutral color, continually variable reflectance and good low end reflectance are obtained while displaying desired information or images or symbols throughout the range of reflectance of the mirror. 
     The above as well as other objects or advantages of the present invention will become apparent from the following description and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view of an automatic rearview mirror embodying the present invention, the mirror being particularly adapted for use as an outside rearview mirror on automotive vehicles; 
     FIG. 2 is an enlarged cross sectional view, with portions broken away for clarity of illustration, of the automatic rearview mirror illustrated in FIG. 1; 
     FIG. 3 is an simplified cross sectional view of the information or image display means incorporated in the mirror illustrated in FIGS. 1 and 2; and 
     FIG. 4 is a simplified cross sectional view of another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     In general, in automatic rearview mirrors embodying the present invention, the rearview mirror is comprised of a thin layer of a chemical solution sandwiched between two glass elements. As the chemical layer is electrically energized, it darkens and begins to absorb light. The higher the voltage, the darker the mirror becomes. When the electrical voltage is decreased to zero, the mirror returns to its clear state. Automatic rearview mirrors embodying the present invention may incorporate light sensing electronic circuitry of the type illustrated and described in U.S. Pat. No. 4,917,477, issued Apr. 17, 1990, for Automatic Rearview System for Automotive Vehicles, and assigned to the assignee of the present invention. Also, the electrochromic components of mirrors embodying the present invention may be of the type disclosed in U.S. Pat. No. 4,902,108, issued Feb. 20, 1990, for Single-Compartment, Self-Erasing, Solution-Phase Electrochromic Devices, Solutions for Use Therein, and Uses Thereof, and assigned to the assignee of the present invention. The entire disclosures of U.S. Pat. Nos. 4,917,477 and 4,902,108 are incorporated herein by reference. 
     An electrochromic mirror, generally designated 10, embodying the present invention is depicted in simplified cross-section in FIG. 2. Since some of the layers of the mirror are very thin, the scale has been distorted for pictorial clarity. As shown in FIG. 2, the electrochromic assembly 11 includes a sealed chamber 12 defined by a clear front glass 14, an edge seal 16, and a clear rear glass 18 having a conductive/reflective layer 20. A chemical solution 22 having the desired electrochromic properties fills the chamber 12, and a transparent conductive layer 24 is provided on the second surface of the front glass 14. The layers 20 and 24 may be connected, for example, to electrical control circuits as described in the aforementioned patents. Light rays enter through the front glass 14, the transparent conductive layer 24, and the electrochromic layer 22, before being reflected from the conductive reflective layer 20 provided on the third surface of the mirror glass layer 18. Light in the reflected rays exit by the same general path traversed in the reverse direction. Both the entering rays and the reflected rays are attenuated in proportion to the degree to which the electrochromic solution 22 is light absorbing. When the electrochromic solution 22 is highly light absorbing, the intensity of the exiting rays is diminished, the dim image remaining being from light rays which are reflected off of the front and back surfaces of the front glass 14. Thus, the basic structural elements of the electrochromic assembly include two electrode-bearing sides or walls, a seal 16, which spaces apart and holds the walls in substantially parallel relationship in an assembled device, and which surrounds a volume which in an assembled device is comprised of electrode layers on the electrode-bearing walls as well as the circumferential inside walls 28 of the spacing and sealing layer 16. The volume of the chamber 12 may be filled with any of the solutions disclosed in U.S. Pat. No. 4,902,108 which have reversibly variable transmittance in the operation of the device, the solution in the chamber 12 being in contact with both electrode layers 20 and 24 during operation of the mirror. 
     With reference to FIG. 2, a preferred arrangement for connecting the layers 20 and 24 to a power source is illustrated. In this arrangement, the two electrode-bearing front and rear glass plates 14 and 18 are displaced in opposite directions, laterally from, but parallel to the chamber 12 in order to provide exposed areas 30 and 32. In the embodiments of the invention illustrated in the drawings, electrically conductive spring clips 34 are provided which are placed on the coated glass sheets to make electrical contact with the exposed areas of the conductors 20 and 24, respectively. Suitable electrical conductors (not shown) may be soldered or otherwise connected to the spring clips so that desired voltage may be applied to the device from a suitable power source, it being understood that other means for making electrical contact with the conductors 20 and 24 may be utilized if so desired. 
     As illustrated in the drawings, automatic rearview mirrors 10 embodying the present invention include a bezel 36, the electrochromic assembly 11 previously described, a heater 38, and a mirror back 40 which is adapted to snap into an outside mirror housing (not shown) that may be of any desired configuration, the outside mirror housing being supported on the outside of the automotive vehicle in any desired or conventional manner whereby the field of view of the mirror may be adjusted by the driver of the vehicle in a conventional manner, as for example through manual adjustment or by mechanical or electrical means of the type conventionally provided on modern day automobiles. 
     As shown in FIGS. 1 and 2, the bezel 36 surrounds the electrochromic assembly 11 in a circumferential manner, the bezel 36 overlying the electrochromic assembly 11 so as to conceal the edge portions thereof including the electrically conductive spring clips 34. The bezel includes an exposed, curvilinear main body portion 42 which extends around the entire circumference of the electrochromic mirror assembly 11. The main body portion 42 includes a flat surface 44 which may be sealed to the exposed surface 46 of the glass element 14 through the agency of a suitable glass sealant. The bezel 36 also includes a skirt portion 50 which extends around the entire periphery of the side edges of the electrochromic assembly 11 and also overlies the outside wall of the mirror back 40. The bezel itself is preferably injection molded from a plastic suitable for exterior automotive use. 
     If desired, outside mirror assemblies embodying the present invention may also include the electrical heater 38 which functions to defrost the mirror, the heater 38 preferably being a full surface heater, or the mirror assemblies may be provided with a back member which may be black or other desired color. 
     The mirror back 40 is preferably formed of the same material as the bezel, the mirror back 40 including a centrally disposed support plate portion 54 surrounded by an upstanding flange wall portion 56 integrally joined to the support plate portion by a bight portion 58. The heater 38 is preferably adhered to the adjacent surface of the glass plate 18 through the agency of a non-corrosive pressure sensitive adhesive or film. 
     In the embodiment of the invention illustrated in FIGS. 1, 2, and 3, in order to display the desired information or image or symbol on the mirror, an electrically nonconductive material 60, such as nonconductive ink, is used to define the information or image or symbol, the nonconductive material 60 extending between the opposing surfaces of the conductive layers 20 and 24 so that the nonconductive material occupies the space that would normally be occupied by the electrochromic material in the area forming the information, image or symbol. With such a construction, coloring of the electrochromic material does not occur in the area occupied by the information, image or symbol, but the information, image or symbol is clearly visible at all times. 
     Another embodiment of the invention is illustrated in FIG. 4. In this embodiment of the invention, the desired information or image or symbol 160 is formed of an electrically conductive material, such as a conductive carbon filled paste, that contrasts with the conductive layers 20 and 24. The electrically conductive material is applied, as by printing, to the conductive layer 20 and extends partially into the chamber 112 occupied by the electrochromic material but does not contact the conductive layer 24 or otherwise short-circuit the conductive layers 20 and 24. With such a construction, the electrochromic material colors and clears uniformly while the information, image or symbol is clearly visible at all times. 
     While preferred embodiments of the invention have been illustrated and described, it will be understood that various changes and modifications may be made without departing from the spirit of the invention.