Abstract:
The invention is related to a rear view mirror formed by a plastic glass structure and mirror housing. The plastic glass allows smooth edges and a bezel free appearance of the mirror. The plastic glass allows in addition to shine through the mirror body to create different types of illumination in the passenger&#39;s cabin.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention is based on a priority patent application EP 08103353.2 which is hereby incorporated by reference. 
         [0002]    The invention is related to an interior rear view mirror which is designed in plastic material and has smooth edges. 
         [0003]    The internal rear view mirror has at least in some transparent areas that allow the installation of illumination elements to shine through. 
       STATE OF THE ART 
       [0004]    Internal rear view mirror are defined e.g. by the regulations of ECE 324 Regulation 46. An internal rear view mirror has a couple of requirements as the field of vision which must be at least a 20 m wide flat horizontal portion of the road. One of the requirements is related to the passenger security and requests that the edges of the internal rear view mirror must be rounded to a radius not less than 2.5 mm. 
         [0005]    In result of this requirement the internal rear view mirror known in the art often shows designs with a plastic mirror case defining a front opening. The front opening includes the reflecting glass which is fixed by a retaining bezel. The retaining bezel is form of plastic material to fulfill safety requirement and the minimum radius of the regulations. 
         [0006]    The appearance of the internal rear view mirror with the bezel surrounding the reflecting element is not satisfying some design request. 
         [0007]    It is known from EP 07440321 B1 especially from FIGS. 18-21 to design an internal rear view mirror without a retaining bezel. The reflecting element is snapped in the peripheral side walls of the mirror case which forms lips, rounded in the required radius. 
         [0008]    The proposed solution is using a glass mirror to be pressed between the molded side wall lips. The known solution includes a means to illuminate the interior of a vehicle, read lamps and ambient light. The internal rear view mirror is prepared to receipt light module device and the lenses so that light shines through the mirror housing. 
         [0009]    It is also know in the art by DE 3049169 to form a plastic glass for an internal rear view mirror. The plastic glass is snapped into place and is tightly connected to the mirror housing. The plastic glass is coated with a reflecting layer on the inner surface of the mirror. 
         [0010]    A disadvantage is the connection with the tongue and groove joint that needs a precisely molding to connect the mirror housing part with the mirror without a visible slit. 
       SUMMARY OF THE INVENTION 
       [0011]    The inventive internal rear view mirror consists of mirror housing and a one piece front plastic glass that has at least one side piece. The fully transparent plastic glass is molded in one piece and coated with a reflective layer at least partly. 
         [0012]    The internal rear view mirror according the invention allows a very simple mirror design including only tow main parts: the mirror housing and the front plastic glass without additional parts as lenses or bezels. The transparent plastic glass is combining the function of the mirror glass, the function of the lenses built in the mirror housing in prior art and the mirror housing with smoothed edges. 
         [0013]    With the internal rear view mirror according the invention a light weighted mirror is created. The high flexibility of molded plastic glass allows a lot of different bezel free designs of the internal rear view mirror. The small weight of the interior mirror allows to ease the mirror base structure or to support further functionalities as GPS receiver, wireless connections, etc without dramatically increase of weight. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  shows a plane view of a internal rear view mirror 
           [0015]      FIG. 2  shows a cross section of the internal rear view mirror 
           [0016]      FIG. 3  shows a first embodiment of the invention 
           [0017]      FIG. 4  shows a second embodiment of the invention 
           [0018]      FIG. 5  shows a schematic illumination 
           [0019]      FIG. 6  shows a second schematic illumination 
           [0020]      FIG. 7   a  to  b  show deforming production process 
           [0021]      FIG. 8  shows deforming of a second embodiment 
           [0022]      FIG. 9  shows the side piece structure to form a lens 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0023]      FIG. 1  shows schematically an internal rear view mirror from the front side. A mirror housing  1  is attached to a mirror base  2  which is connected to vehicle&#39;s roof or wind screen. The mirror housing  1  has an opening to the interior of the vehicle in which front plastic glass  3  is inserted. 
         [0024]    Behind the front plastic glass  3  in the mirror housing a light module  4  is installed either at the backside or the base side of the mirror housing. The light module  4  is known in prior art and comprises a printed circuit board with bulbs and or LEDs and reflectors. In a preferred embodiment only LEDs are installed that works through the lifetime of the inventional mirror and must not be replaced. 
         [0025]      FIG. 2  is a cross section of the interior mirror of  FIG. 1 . The mirror housing  1  and the front plastic glass  3  form a closed cavity in which the electrical and or the electronically elements and circuits are placed. As an example a part of a light module  4  is shown in the cavity. The front plastic glass forms the front plate of the interior mirror and has a side piece  5  forming together an L-form. The edges are smoothed to follow the regulations and design rules. It is possible to have thick front plastic glass with a radius which is much more than the regulations requests. The front plastic glass  3  is one piece closing the front and the base of the internal rear view mirror. The front plastic glass  3  is coated with a reflective layer  6 , normally a metal layer. The L-formed front plastic glass has two functions: to be the mirror for the internal rear view mirror and to be the lens for the interior illumination means. To achieve this function the front plastic glass is formed as a one-piece plastic glass highly transparent and stable. In a further step the plastic glass is coated with metal layer  6  on the front side covering the visible part for passengers looking perpendicular on the surface in direction of arrow  7 . This means that the internal rear view mirror appears without a bezel and fully reflecting. But this means also that the section between the non transparent mirror housing  1  and the front plastic glass  3  remains transparent and emits light if light module in the mirror housing is activated. This edge illumination is sketched with arrows  8 . Also within the side piece  5  light is emitted through the transparent front plastic glass  3 . 
         [0026]    The two main parts of the mirror the housing  1  and the front plastic glass  3  are connect together in a way person skilled in the art would choose. For example a welding or gluing connection is possible. 
         [0027]      FIG. 3  is a second embodiment of the internal rear view mirror. In this example the references describes the same mirror design as in  FIG. 2 . The difference is the surface on which the reflective metal layer is coated. In this embodiment the metal layer  6  is on the inner surface of the front plastic glass  3 . 
         [0028]    As a result the mirror housing  1  would be visible at the lower horizontal part of the mirror from the passengers. In this embodiment this problem is solved with a small area of additional reflective coating  6  on the front side. 
         [0029]    In this embodiment the connection between mirror base and mirror housing on the top must achieved in a way not to destroy the metal layer of the reflective coating  6 . Alternative also an additional reflective coating area on the outer surface of the front plastic glass is possible covering the edges of the front side. This solution eases the connection between front plastic glass and mirror housing. 
         [0030]    The thickness of the reflective coatings depends on the material and the color that should achieved. In  FIG. 3  edge illumination appears by guiding the light in the reflective element. 
         [0031]      FIG. 4  is another embodiment of the invention comprising two side pieces of the front plastic glass covering the bottom and the top of the internal rear view mirror. The front plastic glass is unshaped. This embodiment is improving the indirect illumination of the internal rear view mirror which could be seen in  FIG. 6  with dotted lines. 
         [0032]      FIGS. 5 and 6  shows the appearance of the lighted internal rear view mirror with different areas of illumination A and B mark the read lamp function and C is an ambient light following different designs. 
         [0033]    The front plastic glass is a material transparent for visible wavelengths and able to guide visible light to a certain extend. Light is coupled in and coupled out by special surface structures as ribs and edges. The surface structures are positioned beside the optical plan surface of the front plastic glass which is used as a mirror. 
         [0034]    The process to mould the plastic glass is published in the EP 1412158. 
         [0035]    The process includes the steps of first providing an injection mould machine. The injection molding machine includes a cavity therein, for forming a transparent plastic article simulating the transparency of glass. The mould includes a pressure sensing and regulating apparatus. The mould is thereafter closed and a clear plastic material is injected into the mould through a port. A portion of the mould is used to pressurize the mould material back into the injection port. After the material is partially injected back into the injection port, the mould is held at a predetermined pressure for optimizing optical properties of the plastic material, to provide a clear transparent plastic material which has optical properties similar to glass. 
         [0036]    In the device there is provided a first mould platen and a second mould platen. The first mould platen includes the cavity for production of the final finished part. A second movable piston portion is provided, which includes a cavity, which is adjustable by movement of the piston. The pressure in cavity is adjusted by way of the hydraulic smaller control piston, which is set forth for use in a control system, which hydraulically can compress or adjust the hold position of the moveable portion. A proportional valve may be utilized in the control system for controlling the adjustment of the pressure in the mould cavity. A pressure sensor is utilized to determine the pressure in the cavity, for purposes of the hold pressure in the subject process. After this, the proper pressure is determined and the mould cavity is held at this pressure by way of the control system linked to the proportional valve. 
         [0037]    Referring to the examples of  FIGS. 7   a  and  b  and  FIG. 8 , there is shown a sample mirror in which various contours of the mirror can be presented as may be desired. This gives options which were hard to create using glass type mirrors or the like. The examples as shown in  FIG. 7  b with one side piece  5  can be molded in one process and ejected with a piston contacting the side piece of the plastic glass. The design as shown in  FIG. 7   a  has a adjacent rim which is molded together with the plastic glass element. The rim is used as a “loosed” part. During the deform process ejectors eject the article via these rims. Afterward the rims are cut off. With a solution like this the appearance of piston stamps on the transparent plastic glass is avoided. 
         [0038]    A design as shown in  FIG. 8  shows a drip mould which means that the molding form must include pistons and pins to remove the article form the cavity. 
         [0039]    Preferably, the mould is then held at a pressure of generally from about 900 bar to about 1800 bar preferably from about 1000 to about 1800 bar and preferably from about 1000 to about 1200 bar. 
         [0040]    It has been found that by using these steps, a glass-like transparency can be obtained. Utilizing these steps helps relieve internal tension in the material therefore removing barriers to optical clarity which otherwise might arise. 
         [0041]    Mould temperatures vary depending on the material used. Typically, suitable temperatures are from about 80 to 120 [deg.] C. A most preferred temperature of about 80 [deg.] C. is utilized in the process. 
         [0042]    Typical plastics used in the present invention include optical grade injection moldable material, optical grade polycarbonates, methacrylates or methacrylate modified polycarbonates. Suitable materials are obtainable from General Electric, for instance, plastics sold under the trade designations MAKROLON 2207 and LEXAN LSI are particularly suitable in processes of the present invention. Also, it is necessary to provide optical quality polished mould surfaces to maintain the optical properties of the finished part. The optical surface can be restricted to the plane part of the reflective element. The side piece  5  of the front plastic glass  3  can be designed to appear like frosted glass. 
         [0043]    The surface  5   a  as shown in  FIG. 7   a  is the surface through which illuminating light is emitted. The frosted glass effect achieved by a different structured surface in the molding tool emits a smooth light. 
         [0044]    To provide read lamps the lenses of this read lamps A and B are also molded directly by structuring the tool. Therefore a Fresnel lens can be produced in the same molding step.  FIG. 9  shows an embodiment of the front plastic glass seen from the bottom side of the mirror. The surface  5   a  of the front plastic glass  3  includes lenses  16  and a structure  17  out-coupling of light. The surface  5   a  is in this embodiment not fully transparent. 
         [0045]    Subsequent heat treatments of the part which may occur due to protective or reflective coatings which may be applied do not detrimentally affect or degrade the mirrors of the present invention. This is due to the step of maintaining the part under the pressures specified at molding temperature. Generally, dwell times at temperature are from about 0.1 to 60 seconds. Typical dwell times at temperature are from about 10 to 50 seconds, with preferred dwell times being from about 18 to 25 seconds. 
         [0046]    Because the plastic is allowed to harden at an elevated temperature and pressure, subsequent treatments requiring heat, such as adding reflective coatings, do not adversely affect the optical properties of the plastic. 
       Legend 
       [0000]    
       
           1  Mirror Housing 
           2  Mirror Base 
           3  Reflective Element 
           4  Light Module 
           5  Side Piece of Reflective Element 
           6  Reflective Coating 
           7  Pane View 
           8  Edge Illumination 
         A, B Read Light 
         C Ambient Light 
         Rim 
           10  Piston 
           11  Second Plastic Glass 
           12  Inter glass Space 
           13  Electrochromatic Material 
           14  Fixing and Isolating Mean 
         Lens 
         Surface Structure 
         LED