Abstract:
An emergency information sign ( 10 ) comprising a base substrate ( 12 ) and an indicia layer ( 14 ) positioned over the base substrate ( 12 ). Exposed areas ( 24 ) of the base substrate ( 12 ) and covering areas ( 26 ) of the indicia layer ( 14 ) together form emergency information indicia. The base substrate ( 12 ) and the indicia layer ( 14 ) each carry phosphorescent materials ( 20, 22 ), which absorb and store light from a primary light source ( 16/18 ) and emit this stored light during dark conditions.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Nos. 60/552,596 and 60/621,859 filed on Mar. 12, 2004 and Oct. 25, 2004, respectively. The entire disclosures of these provisional applications are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally, as indicated, to an emergency information sign and, more particularly, to an emergency information sign comprising a base substrate and an indicia layer positioned over the base substrate.  
       BACKGROUND OF THE INVENTION  
       [0003]     Phosphorescent material is commonly employed as a passive light source to provide light when a primary source of light (e.g., an electrically powered light source and/or sunlight) is unavailable. When primary light is being supplied to a viewing environment by the primary light source, the phosphorescent material absorbs this primary light and then emits the absorbed light in the absence or minimization of the primary light. Thus, the phosphorescent material can provide light in an emergency situation without batteries and/or on-premise generators being employed. For this reason, phosphorescent material will often be used to make emergency information signs, which must convey emergency indicia (e.g., the word “EXIT” or an arrow pointing in an appropriate escape direction) in dark conditions.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention provides an emergency information sign which incorporates phosphorescent material in both a base substrate and an indicia layer to clearly convey emergency indicia during dark conditions.  
         [0005]     More particularly, the present invention provides an emergency information sign comprising a base substrate and an indicia layer positioned over the base substrate. The base substrate has areas which are exposed and the indicia layer has areas which cover the base substrate, these areas together forming emergency information indicia. The base substrate and the indicia layer each carry phosphorescent materials which absorb and store light from a primary light source and which emit this stored light during dark conditions.  
         [0006]     The emission characteristics of the base substrate can differ from those of the indicia layer, whereby the emergency information indicia can be clearly distinguished during dark conditions. This can be accomplished by the emission rate of the base substrate differing from the emission rate of the indicia layer and/or by the emission color of the base substrate differing from the emission color of the indicia layer. Additionally or alternatively, the level of phosphorescent material carried by the base substrate differing from the level of the phosphorescent material carried by the indicia layer.  
         [0007]     The indicia layer preferably has a high optical transmittance (e.g., at least 50%, at least 60%, at least 70%, and/or at least 80%). The base substrate can have an optical transmittance less than that of the indicia layer, and the sign can be “front-lit” with primary light passing through the indicia layer to the base substrate. Alternatively, the base substrate can have an optical transmittance the same or greater than that of the indicia layer, and the sign can be “back-lit” with primary light passing through the base substrate to the indica layer.  
         [0008]     The exposed areas of the base substrate can form emergency information indicia and, if so, the indicia layer may be made by positioning a matrix from a die-cut sheet on the base substrate. The covering areas of the indicia layer can instead form the emergency information indicia and, if so, the indicia layer may be made by positioning die-cut indicia on the base substrate. Alternatively, the indicia can be printed or painted (with a mask) onto the base substrate.  
         [0009]     These and other features of the invention are fully described and particularly pointed out in the claims. The following description and drawings set forth in detail certain illustrative embodiments of the invention, which are indicative of but a few of the various ways in which the principles of the invention may be employed.  
     
    
     DRAWINGS  
       [0010]      FIG. 1  is a perspective view of an emergency information sign according to the present invention.  
         [0011]      FIG. 1A  is a close-up view of the base substrate of the emergency information sign of  FIG. 1 .  
         [0012]      FIG. 1B  is a close-up view of a modified base substrate of the emergency information sign of  FIG. 1 .  
         [0013]      FIG. 1C  is a close-up view of the indicia layer of the emergency information sign of  FIG. 1 .  
         [0014]      FIG. 1D  is a close-up view of a modified indicia layer of the emergency information sign of  FIG. 1 .  
         [0015]      FIG. 2  is a perspective view of another emergency information sign according to the present invention.  
         [0016]      FIG. 3  is a perspective view of another emergency information sign according to the present invention.  
         [0017]      FIG. 4  is a perspective view of another emergency information sign according to the present invention.  
         [0018]      FIGS. 5A-5D  are views schematically showing a method of making an emergency information sign according to the present invention.  
         [0019]      FIG. 6  is a view schematically showing another method of making an emergency information sign according to the present invention.  
         [0020]      FIG. 7  is a view schematically showing another method of making an emergency information sign according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0021]     Referring now to the drawings, and initially to  FIG. 1 , an emergency information sign  10  according to the present invention is shown. The sign  10  comprises a base substrate  12  and an indicia layer  14  positioned over the base substrate  12 . The sign  10  is oriented so that the indicia layer  14  is closest to a primary light source, which can be either an artificial light source  16  and/or an ambient light source  18 .  
         [0022]     The base substrate  12  carries a phosphorescent material  20  that may be in the form of particles coated thereover ( FIG. 1A ) or embedded therein ( FIG. 1B ). It may be noted that, although in the illustrated embodiment the base substrate has a sheet-like shape, other structures are certainly possible. Specifically, for example, the base substrate  12  could comprise a portion of a wall or floor over which the indicia layer  14  is placed. Accordingly, the substrate could be made of a variety of materials, provided that the substrate material is compatible with coating, embedding, or otherwise carrying the phosphorescent material  20 .  
         [0023]     The indicia layer  14  carries a phosphorescent material  22  that may be in the form of particles coated thereover ( FIG. 1C ) or embedded therein ( FIG. 1D ). In the sign  10  shown in  FIG. 1 , the indicia layer  14  can be made from a clear polymer (Polycarbonate, PMMA, Urethane, Vinyl, etc.). The density of the phosphorescent material  22  in the layer  14  is such that it has a relatively high optical transmission, such as at least 50%, at least 60%, at least 70%, and/or at least 80%. (Optical transmittance refers to the ratio of the light transmitted by the primary light source to the light which passes through the phosphorescent-carrying substrate. An optical transmittance of 0% would correspond to a substrate which allows no optical transmission and an optical transmittance of 100% would correspond to a substrate which is completely transparent.)  
         [0024]     The base substrate  12  has exposed areas  24  that are not covered by the indicia layer  14 , and the indicia layer  14  has areas  26  which cover aligned areas of the base substrate  12 . The areas  24  and the areas  26  together form the emergency information indicia which, in the illustrated embodiment, is the word “EXIT.” In the emergency information sign  10  shown in  FIG. 1A , the areas  24  form the letters E-X-I-T, and the areas  26  form the background for these letters. Alternatively, as shown in  FIG. 2 , the exposed areas  24  of the base substrate  12  can form the background, and the areas  26  of the indicia layer  14  can form the letters E-X-I-T.  
         [0025]     When primary light is emitted from the primary light source  16 / 18 , it passes to the areas  24  of the indicia layer  14  and is absorbed and stored by the phosphorescent material  22  therein. Also, because the indicia layer  14  has a high optical transmission, the primary light also passes to the aligned areas of the base substrate  12  and is absorbed/stored by the phosphorescent material  20  therein. Further, the primary light passes to the exposed areas  26  of the base substrate  12  and is absorbed and stored by the phosphorescent material  20  therein.  
         [0026]     Referring now to  FIGS. 3 and 4 , other emergency information signs  10  according to the present invention are shown. In these signs, the base substrate  12  is closest to the primary light source  16 / 18 , and both the base substrate  12  and the indicia layer  14  have a relatively high optical transmission, such as at least 50%, at least 60%, at least 70%, and/or at least 80%. When primary light is emitted from the primary light source  16 / 18 , it passes to the base substrate  12  and is absorbed/stored by the phosphorescent material  20  therein. The primary light also passes therethrough to the indicia layer  14 , whereat it is absorbed/stored by the phosphorescent material  22  therein. In  FIG. 3 , the areas  24  form the letters E-X-I-T, and the areas  26  form the background for these letters. In  FIG. 4 , the exposed areas  24  of the base substrate  12  form the background, and the areas  26  of the indicia layer  14  form the letters E-X-I-T.  
         [0027]     In the absence of primary light (i.e., in dark conditions), the phosphorescent material  20 / 22  emits the stored light as phosphors, thereby providing passive light. If the emission characteristics of the base substrate  12  and the indicia layer  14  are substantially the same, the areas  24  will appear brighter than the areas  26  because of the “double layer” of emission. (The high optical transmission of the indicia layer  14  allows the passive light created by underlying areas of the base substrate  12  to pass therethrough to the viewing environment.) If the emission characteristics of the base substrate  12  differ from the emission characteristics of the indicia layer  14 , the emergency information indicia can be clearly distinguished during dark conditions. For example, the emission characteristics can be different emission levels and/or different emission colors. Additionally or alternatively, the level of phosphorescent material  20  carried by the base substrate  12  can differ from the level of the phosphorescent material  22  carried by the Indicia layer  14 .  
         [0028]     The overall passive light emission of the emergency information sign  10  (or the combined passive light emission of the base substrate  12  and the indicia layer  14 ) can be at least 15.0 mcd/m 2  at ten minutes and at least 2 mcd/m 2  at sixty minutes, and/or can be an emission of at least 20.0 mcd/m 2  at ten minutes and at least 2.8 mcd/m 2  at sixty minutes. These emission levels are necessary to satisfy IMO and ASTM standards, respectively, for emergency lighting requirements. The sign  10  can have an emission of at least 30 mcd/m 2  at ten minutes, at least 40 mcd/m 2  at ten minutes, and/or at least 50 mcd/m 2  at ten minutes.  
         [0029]     The phosphorescent material  20 / 24  can be a phosphorescent phosphor including a matrix expressed by MAI 2 O 4  in which M is calcium, strontium, or barium, or in which M is magnesium activated by calcium, strontium, barium, and/or europium. These phosphorescent phosphors show excellent photo-resistance and possess extremely long afterglow characteristics. Such phosphorescent phosphors are disclosed and described in U.S. Pat. No. 5,424,006, the entire disclosure of which is hereby incorporated by reference. Another phosphor having intense and persistent afterglow characteristics is disclosed in U.S. Pat. No. 5,770,111, the entire disclosure of which is also hereby incorporated by reference. By using intense and/or persistent phosphors, a low density of particles can be used. This may prove to be especially useful when the base substrate  12  and/or the indicia layer  14  need to have a high optical transmission, but a high emission rate is also desired.  
         [0030]     The emergency information sign  10  can be made by the process shown schematically in  FIGS. 5A-5D . Specifically, a sheet  40  is provided having the desired emission and transmission characteristics of the indicia layer  14 . ( FIG. 5A .) The emergency information is die cut from the sheet  40  to form cut portions  42  and a matrix  44 . ( FIG. 5B .) For the emergency information signs  10  shown in  FIGS. 1 and 3 , the cut portions  42  are discarded and the matrix  44  is placed on the substrate  12 . ( FIG. 5C .) For the emergency signs  10  shown in  FIGS. 2 and 4 , the matrix  44  is discarded and the cut portions  42  are placed on the base substrate  12 . ( FIG. 5D .) A clear adhesive can be used to secure the indicia layer items  42 / 44  to the base substrate  12 .  
         [0031]     As shown in  FIG. 6 , the emergency signs  10  of  FIGS. 2 and 4  can also be made by printing the areas  26  onto the base substrate  12 . Alternatively, as shown in  FIG. 7 , a mask  50  having openings  52  corresponding to the areas  26  could be placed on the base substrate  12  and then be spray painted to form the areas  26 . A compound  54  having the desired emission, transmission, and other characteristics of the indicia layer  14  would be used as the printing and/or painting fluid.  
         [0032]     One may now appreciate that the present invention provides an emergency information sign  10  which incorporates phosphorescent material  20 / 22  in both a base substrate  12  and an indicia layer  14  to clearly convey emergency indicia during dark conditions. Although the invention has been shown and described with respect to certain preferred embodiments, it is evident that equivalent and obvious alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification. The present invention includes all such alterations and modifications and is limited only by the scope of the following claims.