Abstract:
A self-illuminating glazing panel suitable for use in an automotive vehicle is provided for better night and dusk visibility for safety purposes and for brighter appearance during the day. The self-illuminating glazing panel integrates a luminescent layer, containing phosphorescent or fluorescent pigments or dyes, with a plastic substrate. The luminescent layer allows the panel to glow during the evening and night hours upon excitation by external light sources, such as headlamps and streetlights.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a plastic glazing panel for use as an automotive window. More specifically, the invention relates to a self-illuminating glazing panel that integrates a layer of luminescent ink comprising a phosphorescent or a fluorescent pigment with a polymeric substrate. 
         [0003]    2. Background of the Invention 
         [0004]    Plastic materials are used for manufacturing various automotive parts and components such as B-Pillars, headlamps, and various panels. Some plastic materials, such as polycarbonate, offer superior resistance to fracture and/or dislodgement in case of accidents and hence may be used as glazing panels for the windows and sunroofs of automotive vehicles. Plastic materials give more freedom in the style and shape of the glazing panel which in effect provides significant freedom in regards to the design of an automotive window. Furthermore, plastic materials may be combined with coating systems to add different functionalities to the glazing panels. 
         [0005]    It currently has become popular with the end-user to use colored and illuminating bands in conjunction with glass window panels for both styling and safety purposes. A bright band on a vehicle&#39;s window helps increase the visibility of the vehicle to other motorists and pedestrians. The enhanced visibility of such vehicles assists in significantly reducing side and rear-end collisions. Vehicles with bright-banded windows may play a crucial role in avoiding accidents during the evening and night hours. 
         [0006]    The illuminated bands or strips that may be attached to a car&#39;s window or body for decorative or safety purposes are essentially an after-market product. These illuminating bands are typically neither integrated as part of the car body or in the window glazing system. Aftermarket products, such as these illuminating bands, are usually expensive and not tested to meet or maintain the stringent performance conditions required for automotive original equipment. 
         [0007]    Therefore, there is a need for an integrated colored and/or illuminated band into the automotive glazing system in order to insure that there are no detrimental performance effects and to minimize the cost of such a component to the end-user. 
       SUMMARY 
       [0008]    The present invention is directed to a self-illuminating glazing panel suitable for use in an automotive vehicle that provides aesthetic acceptance and better visibility during the night for safety purposes. In one embodiment of the present invention, the self-illuminating glazing panel comprises a plastic substrate, a luminescent layer disposed on the plastic substrate, a weatherable layer affixed to the luminescent layer for reducing the amount of infrared and ultraviolet radiation penetrating into the underlying plastic substrate, and an abrasion resistant layer capable of resisting abrasion upon exposure to external elements. 
         [0009]    Another embodiment of the present invention provides a method for manufacturing a self-illuminating glazing panel. The method comprises forming a self-illuminating glazing panel by molding a plastic substrate from a polymeric resin and printing a layer of luminescent material on the molded plastic substrate. The method further comprises depositing at least one weatherable layer onto the surface of the plastic panel; and depositing at least one abrasion layer onto the weathering layer(s), the abrasion layer providing abrasion resistance to the outwardly facing surfaces of the glazing panel. 
         [0010]    The luminescent layer is integrated with the glazing panel so that the glazing panel glows due to excitation from external light sources during the night, such as head lamps from another vehicle. The glazing panel is preferably self-illuminating and is capable of producing luminescence without requiring any external electrical power source, as is required for electroluminescent materials. 
         [0011]    Automotive safety is one advantage that a self-illuminating glazing panel of the present invention provides by increasing the visibility of the vehicle to other motorists and pedestrians. This in turn may play a crucial role in avoiding accidents during the evening and night hours. A second advantage of the present invention is that a luminescent layer, when integrated with the glazing panel, may give a brighter appearance to the windows or sunroofs during the daylight hours. This effect may enhance the aesthetic appearance of the vehicle to the end-user. 
         [0012]    These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    In the drawings, the same or similar reference numbers identify similar elements. 
           [0014]      FIG. 1  is a partial perspective view of an automotive vehicle incorporating a self-illuminating glazing panel according to the principles of the present invention. 
           [0015]      FIG. 2  is a cross-sectional schematic illustration of a self-illuminating glazing panel according to the present invention wherein a luminescent layer is printed on a plastic substrate. 
           [0016]      FIGS. 3A and 3B  are cross-sectional schematic illustrations of alternative embodiments of the present invention wherein the self-illuminating glazing panel includes a plastic film integrated with the self-illuminating glazing panel using a film insert molding (FIM) technique. 
           [0017]      FIG. 4  is a block diagram showing a process for manufacturing the self-illuminating glazing panel according to another aspect of the present invention. 
           [0018]      FIG. 5  is a block diagram showing an alternative embodiment for the process of manufacturing the self-illuminating glazing panel according to the principles of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIG. 1  shows a portion of an automotive vehicle  10  comprising a body  12  having portions  14 ,  16  defining a rear quarter window opening in which a self-illuminating glazing panel  18 , according to the present invention, is fixed in the conventional fashion, such as with adhesive bonding. A masking body  20  is preferably provided to conceal the adhesive joint. 
         [0020]      FIG. 2  diagrammatically illustrates a cross-sectional view of one embodiment of the self-illuminating glazing panel  18  of the present invention. As shown, the glazing panel  18  comprises multiple layers integrally formed with a plastic substrate  22 , which is a transparent plastic panel having good optical clarity. The plastic substrate  22  forms the base layer for glazing panel  18 . A luminescent layer  24 , printed on plastic substrate  22 , provides a self-illuminating characteristic to the glazing panel  18 . Additionally, an optional functional layer  26  may be printed or deposited on the luminescent layer  24  using any standard technique known to those skilled in the art. The optional functional layer  26  may be comprised of a single layer or multiple sub-layers  25 , with each sub-layer providing a different functionality. For example, one sub-layer  25  may comprise a decorative border (such as the masking body  20  mentioned previously), while a second sub-layer  25  may comprise a heater grid for defrosting the window. The luminescent layer  24  and the optional functional layer  26  are placed on the interior surface of the plastic substrate, which is the surface located to the inside of the automotive vehicle  10 . Overlaid on the exterior side of the plastic substrate  22 , is a weatherable layer  28  that blocks the transmission of ultraviolet radiation, thereby preventing any harmful effects of the radiation on the underlying layers. A second weatherable layer  28 ′ may be optionally provided on the interior of the vehicle. This layer  28 ′ is optional because the interior surface of the glazing panel interacts with substantially less sunlight than the exterior surface of the glazing panel. An abrasion resistant layer  28  forms the outermost layer of the self-illuminating glazing panel, over the weatherable layer  29 , and provides an additional degree of protection for the self-illuminating glazing panel from abrasion, moisture, and other external elements. As with the second weatherable layer  28 ′, a second abrasion layer  29 ′ may be provided on the interior of the glazing panel  18 . 
         [0021]    Preferably, the plastic substrate  22  is transparent. However, it may in some instances be translucent, opaque or a combination of these. The plastic substrate  22  can be formed of a variety of different thermoplastic or thermoset polymeric resins known to those skilled in the art. These polymeric resins include, but are not limited to, polycarbonate, acrylic, polyacrylate, polyester, polysulfone, polyurethane, silicone, epoxy, polyamide, polyalkylenes, acrylonitrile-butadiene-styrene (ABS) as well has copolymers, blends, and mixtures thereof. The plastic substrate  22  may further include various additives such as colorants, Theological control agents, mold release agent, antioxidants, ultraviolet absorbing (UVA) molecules, and infrared (IR) absorbing or reflecting pigments, among others. 
         [0022]    The luminescent layer  24  comprises a phosphorescent or fluorescent ink that is capable of producing luminescence after absorbing radiant energy or other type of energy. The luminescent layer  24  may be a band, strip, border, or decorative pattern applied by screen printing, inkjet printing, mask &amp; spray, or any other technique known to those skilled in the art. The luminescent layer  24  may be cured by air drying, UV absorption, thermal absorption, condensation addition, thermally driven entanglement, or cross-linking induced by cationic or anionic species. 
         [0023]    The phosphorescent or fluorescent ink is preferably formed of a polymeric binder or resin and a phosphorescent pigment, a fluorescent dye, a fluorescent pigment, or a mixture of both, dispersed in a carrier liquid. The carrier liquid may comprise a single solvent or a mixture of solvents. Other additives, such as rheological control agents, antioxidants, surfactants, and biocides, among others, may also be present in the ink. 
         [0024]    The polymeric binder of the phosphorescent or fluorescent ink may be any polymer suitable for adhering to the plastic substrate (base layer)  22  or a plastic film (further discussed below) used in the formation of the self-illuminating glazing panel. Examples of polymeric binders or resins include, but are not limited to polycarbonate, acrylic, polyacrylate, polyester, polysulfone, polyurethane, silicone, epoxy, polyamide, polyalkylenes, acrylonitrile-butadiene-styrene (ABS) as well has copolymers, blends, and mixtures thereof. Preferably, the polymeric binder in the phosphorescent or fluorescent ink is substantially similar to the polymeric resin present in any ink or coating used to form an optional functional layer in the self-illuminating glazing panel, as discussed below. 
         [0025]    Phosphorescent pigments include, but are not limited to strontium oxide aluminates, sulphides of calcium, strontium, zinc, or barium doped with copper, bismuth, or manganese, and radioisotopes, such as Radium or Tritium. A specific example of a phosphorescent pigment is strontium oxide aluminate available as LumiNova® from Nemoto &amp; Co. Ltd. (Tokyo, Japan). 
         [0026]    Suitable fluorescent dyes include, but are not limited to, sodium fluorescein, rhodamine, fluoresceine, resorcinolphthalein, and conjugated derivatives of stilbene and benzimidazole. Fluorescent pigments include, but are not limited to, organic pigments and minerals that absorb short wavelengths and long wavelengths of light. Examples of long wavelength absorbing fluorescent minerals include agate (white-blue), magnesite (white-blue), calcite (red), fluorite (yellow), and scapolite (pink). Examples of short wavelength absorbing fluorescent minerals include ruby (red), halite (red), gypsum (yellow), diamond, and adamite (green). A specific example of an organic fluorescent pigment is the aldazine pigment (yellow) available as Lumogen® Yellow S 0790 from BASF (Germany). 
         [0027]    Phosphorescence is a form of photoluminescence stimulated by the absorption of light in the UV-Vis-NIR spectral region. Phosphorescent pigments absorb light at wavelengths represented by this spectral region, which is then remitted slowly over time, typically as photons of longer wavelengths of light. Phosphorescent pigments are known to “glow in the dark” releasing the absorbed light over minutes or hours after the light source has been removed. When phosphorescent pigments are integrated with a self-illuminating glazing panel of a vehicle, the excitation light source may typically be the headlights of other vehicles, as well as streetlights and other light sources external to the vehicle. 
         [0028]    The phosphorescent effect is highly dependent upon the selection of the pigments, the light absorption properties of the self-illuminating glazing panel, and the intensity of the light absorbed. The type of pigment selected, preferably, absorbs light in a portion of the spectral region that is substantially different than the portion of the region being effectively filtered or absorbed by the plastic substrate, plastic film, or weatherable layer. For example, polycarbonate is an effective filter of any UV radiation having a wavelength below about 380 nanometers. In addition, the photolytic degradation of polycarbonate upon exposure to UV radiation exhibiting a wavelength of 290 to 340 nanometers, requires the weatherable layer to absorb or reflect these wavelengths of light, thereby, protecting the underlying plastic panel and plastic film. Thus, in this specific case, it would be preferred that the phosphorescent pigments present in the luminescent layer absorb a wavelength of light that is greater than about 380 nanometers. 
         [0029]    The luminescent layer may be comprised of a mixture of phosphorescent and fluorescent pigments. In this embodiment, the light absorbed and re-emitted by the fluorescent pigments occurs over a very rapid time frame with respect to the time frame over which light is re-emitted by the phosphorescent pigments. This rapid re-emission of fluorescent light causes the self-illuminating glazing panel to “glow”. 
         [0030]    Fluorescence is a form of photoluminescence that occurs on a substantially faster time scale than phosphorescence. In fluorescence, the emitted light is always of a longer wavelength than the excitation or incident light. The emission of fluorescent light continues to occur as long as the external light source is present. If the exciting radiation is stopped, then the occurrence of fluorescence ceases. A more thorough molecular treatment of both phosphorescence and fluorescence is available to those skilled in the art in the form of a Jablonski Energy Diagram. Similar to phosphorescence, the fluorescent effect is highly dependent upon the selection of the pigments, the light absorption properties of the self-illuminating glazing panel, and the intensity of the light absorbed. The fluorescent pigment utilized in the luminescent layer of a self-illuminating panel preferably absorbs light in a portion of the spectral region different from the portion of the region that is filtered or absorbed by the plastic substrate, plastic film, or the weatherable layer. 
         [0031]    The use of phosphorescent pigments is preferable over the use of fluorescent pigments due to the associated longer timeframe for emitting light. 
         [0032]    An optional functional layer  26  may be placed onto the surface of the luminescent layer  24 . This optional functional layer  26  may provide multiple functionality to the self-illuminating glazing panel  18 . For example, the functional layer  26  may comprise a decorative layer, such as a black-out or fade-out layer in order to hide the bonding system used to adhere the panel to the vehicle. Other functionalities provided by the optional functional layer  26  may include, but are not be limited to, logos, defrosters or heater grids, antennas, solar control, electroluminescence, conductive films, photochromic films, or electrochromic films. The optional functional layer  26  may cure by air drying, UV absorption, thermal absorption, condensation addition, thermally driven entanglement, or cross-linking induced by cationic or anionic species. 
         [0033]    The weatherable layer  28 , which protects the self-illuminating glazing panel from environmental elements, such as UV radiation and moisture, may comprise silicones, polyurethanes, acrylics, polyesters, epoxies, and mixtures or copolymers thereof. It will be apparent to one skilled in the art that the weatherable layer  28  may include other suitable materials that impart weatherability to the self-illuminating glazing panel. Weatherable layer  28  may be extruded, cast as thin films, or applied as a discrete coating. The weatherable layer  28  may be a single layer or a combination of multiple sub-layers  27 . A specific example of a weatherable layer  28  comprising multiple sub-layers  27  includes a combination of an acrylic primer (SHP401, GE Silicones, Waterford, N.Y.) and a silicone hard-coat (AS4000, GE Silicones). The weatherable layer  28  may further comprise additional additives including colorants (tints), rheological control agents, antioxidants, ultraviolet absorbing (UVA) molecules, and IR absorbing or reflecting pigments, among others. Due to the decreased amount of UV radiation impinging on the surface of the window facing the interior of the car, the weatherable layer  28 ′ present on the interior side of the self-illuminating glazing panel is optional. 
         [0034]    The weatherable layer  28  may be applied by dip coating, flow coating, spray coating, curtain coating, or any other techniques known to those skilled in the art. The thickness of the weatherable layer  28  may range from about 2 micrometers to several mils (1 mil=25.4 micrometers), with about 6 micrometers to 1 mil being preferred. The weatherable layer  28  may cure by air drying, UV absorption, thermal absorption, condensation addition, thermally driven entanglement, or cross-linking induced by cationic or anionic species. 
         [0035]    The abrasion resistant layer  29  may comprise a single layer or multiple sub-layers  30 . The abrasion resistant layer  29  may be comprised of aluminum oxide, barium fluoride, boron nitride, hafnium oxide, lanthanum fluoride, magnesium fluoride, magnesium oxide, scandium oxide, silicon monoxide, silicon dioxide, silicon nitride, silicon oxy-nitride, silicon oxy-carbide, hydrogenated silicon oxy-carbide, silicon carbide, tantalum oxide, titanium oxide, tin oxide, indium tin oxide, yttrium oxide, zinc oxide, zinc selenide, zinc sulfide, zirconium oxide, zirconium titanate, or a mixture or blend thereof. Preferably, the abrasion resistant layer  29  is comprised of a composition of SiO x  or SiO x C y H z  depending upon the amount of carbon and hydrogen atoms that remain in the deposited layer. In this regard, the abrasion resistant layer  29  resembles a “glass-like” coating. 
         [0036]    The abrasion resistant layer  29  may be applied by any suitable technique known to those skilled in the art including techniques involving the deposition of a film from reactive species, such as but not limited to those employed in vacuum-assisted deposition processes. Examples of suitable coating processes include, but are not limited to, plasma-enhanced chemical vapor deposition (PECVD), expanding thermal plasma PECVD, plasma polymerization. photochemical vapor deposition, ion beam deposition, ion plating deposition, cathodic arc deposition, sputtering, evaporation, hollow-cathode activated deposition, magnetron activated deposition, activated reactive evaporation, thermal chemical vapor deposition, and any known sol-gel coating process. The thickness of the abrasion layer  29  may range from about 1 micrometer to 1 mil with about 3 micrometers to 10 micrometers being preferred. Optionally, a similar abrasion layer  29 ′ may be applied to the interior of the glazing panel. 
         [0037]    The weatherable layer  28  and abrasion resistant layer  29  may be combined to form a layered glazing system. Examples of layered glazing systems, include but are not limited to the acrylic/silicone/“glass-like” systems offered by Exatec LLC (Wixom, Mich.) as Exatec® 500, Exatec® 900, and Exatec® 900vt glazing systems. 
         [0038]    Another embodiment of the present invention includes the incorporation of a decorative film as part of the various layers in the self-illuminating glazing panel using film insert molding (FIM) techniques. This decorated film may comprise a plastic film along with the luminescent layer and any optional functional layers. In forming the panel, the decorated film is placed onto tooling of an injection mold with the luminescent and optional functional layers facing away from the surface of the tooling and toward the cavity defined by the mold. A plastic resin is then injected into the mold to encapsulate the luminescent layer and any optional functional layer between the plastic resin and the film. 
         [0039]      FIG. 3A  illustrates a diagrammatic cross sectional view of another embodiment of a self-illuminating glazing panel  18  as provided by the present invention and that incorporates the use of a decorated film. In this embodiment, the self-illuminating glazing panel  18  comprises a plastic film layer  31  and a luminescent layer  24  printed on the plastic film layer  31 . An optional functional layer  26  may be printed or deposited on the luminescent layer  24  by any standard technique known to skilled in the art. The plastic substrate  22  is then back molded onto the plastic film. In this embodiment the plastic film is located, relative to the substrate  22 , toward the exterior of the vehicle. The subsequent application of a weatherable layer  28  to the plastic film is preferable in order to block the transmission of ultraviolet radiation to the plastic film. The abrasion resistant layer  29  provides an additional degree of surface-hardening, as well as protection from abrasion, moisture, and other external elements. As with the prior embodiments, an additional weatherable layer  28 ′ and abrasion resistant layer  29 ′ may be applied to the interior side of the substrate  22 . 
         [0040]      FIG. 3B  illustrates a cross-sectional view of a further embodiment of a self-illuminating glazing panel  18  as provided by the present invention. This embodiment is similar to the embodiment described in  FIG. 3A  except that in this embodiment the plastic film  30  is located toward the interior of the vehicle  10 . In order not to obscure the luminescent layer  24 , any optional functional layers  26  are preferably applied to the plastic film  30  prior to the application of the luminescent layer  24  to the film. In this respect, the position of the luminescent layer  24  and any functional layer  26  have been reversed for this embodiment as compared to the embodiment previously described in  FIG. 3A . In substantially all other aspects, the embodiment of  FIG. 3B  is constructed the same as the embodiment of  FIG. 3A . 
         [0041]      FIG. 4  is a block diagram representation of a process for manufacturing a self illuminating glazing panel  18  according to one embodiment of the present invention. At step  41 , a plastic substrate  22  is formed via injection molding of a transparent plastic resin, such as a polycarbonate or acrylic resin. Plastic substrate  22  forms the base layer for the self-illuminating glazing panel  18 . At step  42 , the plastic substrate  22  is removed from the mold, inspected, and any preliminary processing is carried out such as cleaning, which includes the elimination of any static electrical charges. At step  43 , the luminescent layer  24  is printed onto the plastic substrate  22 . 
         [0042]    In a preferred embodiment, the luminescent layer  24  is printed by a screen printing process. In the screen printing process, a fine mesh screen equipped with a stencil according to the desired shape of the luminescent layer  24 , is placed parallel with the plastic substrate  22 . The screen is then deposited with luminescent ink, followed by forcing of the luminescent ink through the openings of the stencil on the screen using a squeegee that is drawn across the surface of the screen. After the squeegee passes the stencil region, the tension of the stretched screen along with the off-contact distance between the screen and the plastic substrate  22  allows the screen to separate from the surface of the substrate leaving the luminescent layer  24  deposited onto the surface of the substrate. It will be apparent to those skilled in the art that other techniques such as inkjet printing or mask and spray may also be used for providing the luminescent layer  24  onto the plastic substrate  22 . 
         [0043]    At step  44 , any optional functional layers  26  are applied over the luminescent layer  24 . A functional layer  28  can be applied by screen printing, inkjet printing, mask &amp; spray, spray coating, or any other techniques known to those skilled in the art. At step  45 , the weatherable layer  28  is applied to the glazing panel. The weatherable layer  28  may be applied by dip coating, flow coating, spray coating, curtain coating, or any other techniques known to those skilled in the art. At step  46 , the abrasion layer  29  is applied to the glazing panel. The abrasion layer  29  is applied by any suitable technique known to those skilled in the art, including techniques involving the deposition of a film from a reactive species, e.g., vacuum-assisted deposition processes. At step  47 , both a final inspection and finishing of the self-illuminating glazing panel  18  are carried out. The finishing of the self-illuminating glazing panel may include, but need not be limited to, such operations as the sanding or milling of panel edges, the attachment of positioning clips, spacers, or fasteners, the application of an adhesive primer and adhesive, or the cutting of holes for attachments, such as wipers. 
         [0044]      FIG. 5  is a block diagram representation of a process for preparing a self-illuminating glazing panel  18  according to another embodiment of the present invention. At step  51 , the luminescent layer  24  is printed onto a plastic film. In a preferred embodiment, the luminescent layer  24  is printed via a screen printing process. It will be apparent to those skilled in the art that other techniques, such as inkjet printing or mask and spray, may also be used for printing the luminescent layer  24  onto the plastic film. At step  52 , an optional functional layer  26  is applied over the luminescent layer  24 . The optional functional layer  26  can be applied by screen printing, inkjet printing, mask &amp; spray, spray coating, or other techniques known to those skilled in the art. Steps  51  and  52  may be reversed in sequence depending upon if the plastic film faces the exterior of the vehicle as depicted in  FIG. 3A  or interior of the vehicle as depicted in  FIG. 3B . 
         [0045]    At step  53 , the decorated, plastic film is placed into the cavity of a mold and the plastic substrate  22  is back molded onto the film, thereby encapsulating the luminescent layer  24  and any optional functional layers  36 . This molding process is known to those skilled in the art as film insert molding (FIM). At step  54 , the molded plastic substrate  22  is removed from the mold, inspected, and any preliminary processing is carried out such as cleaning, which includes the elimination of static electrical charges. At step  55 , the weatherable layer  28  is applied to the glazing panel. The weatherable layer  28  may be applied by dip coating, flow coating, spray coating, curtain coating, or any other technique known to those skilled in the art. At step  56 , the abrasion resistant layer  29  is applied to the glazing panel. The abrasion resistant layer  29  may be applied by any suitable technique known to those skilled in the art including but not limited to techniques involving the deposition of a film from a reactive species, e.g., a vacuum-assisted deposition process. At step  57 , both a final inspection and finishing of the self-illuminating glazing panel  18  are carried out. 
         [0046]    In as much as the foregoing disclosure is intended to enable one skilled in the pertinent art to practice the present invention, it should not be construed to be limited thereby, but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.