Abstract:
The present invention comprises a device for revealing a message or image responsive to temperature changes of approximately 5° F. (3° C.). A thermochromic leuco dye is applied to a surface that is positioned for contact by an outside heating or cooling source. The thermochromic leuco dye reveals an intended message or image when the temperature is changed sufficiently.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority based on provisional patent application Ser. No. 60/757,767 filed Jan. 10, 2006, the entire content of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates generally to the use of thermochromic leuco dyes on surfaces for revealing a message when the temperature of the dye is changed by a predetermined amount. 
       BACKGROUND AND SUMMARY OF THE INVENTION 
       [0003]    Thermochromic leuco dyes (“LDs”) are well known and are characterized as changing from a specified color to an invisible or clear appearance when their temperature is raised approximately 5° F. (3° C.), and changing back to the specified color when the temperature drops back down. LDs can be found in a variety of forms, including powders, slurries, and water-based inks. 
         [0004]    LDs have been used to indicate a rise in temperature in items as diverse as battery testers, microwave sensors, and Nerf® footballs. The LDs in the battery testers have been used to indicate the power remaining in the battery. The LDs in the microwave sensors have been used to indicate that a substance has been warmed to the desired temperature. And LDs have been used as mere novelties in things such as Nerf® footballs to display a different color when touched by a human hand. 
         [0005]    But LDs have not been used to reveal images or communicate messages to an intended recipient, as is disclosed in the present application. More specifically, the present invention comprises a surface for application of a LD, wherein the surface is positioned so as to be contacted by an outside heating source to reveal an intended image or message when the temperature is changed sufficiently. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    A more complete understanding of the present invention may be had by reference to the following Detailed Description when taken in connection with the accompanying Drawings, wherein: 
           [0007]      FIG. 1  is a perspective view of the first embodiment of the present invention wherein a thermochromic leuco dye is applied to a surface comprising a urinal mat; 
           [0008]      FIG. 2A  is a perspective view of the surface of the urinal mat shown in  FIG. 1  prior to being contacted by the heating source; 
           [0009]      FIG. 2B  is a perspective view of the surface of the urinal mat shown in  FIG. 1  while being contacted by the heating source, and showing the message being revealed; 
           [0010]      FIG. 3  is a perspective view of a second embodiment of the present invention, showing a surface upon which a thermochromic leuco dye is applied on a standard urinal mat having a deodorant cake within an enclosure; 
           [0011]      FIG. 4  is a perspective view of a third embodiment of the present invention, showing a surface upon which a thermochromic leuco dye is applied being positioned within a standard toilet to assist in toilet-training young males; and 
           [0012]      FIG. 5  is front view of a fourth embodiment of the present invention, showing a surface upon which a thermochromic leuco dye is applied being positioned on a standard automobile dashboard. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring now to the drawings, an in particular to  FIG. 1 , a urinal mat  10  is shown positioned over an opening of a drain  12  of a urinal  14 . The urinal mat  10  comprises a plurality of perforations  16  for facilitating the evacuation of the contents of the urinal  14  through the drain  12 . The urinal mat  10  may be constructed of any substance that is impermeable to liquid, such as plastic or rubber, so that the urinal mat  10  does not retain the liquids that are directed thereonto by an individual who is using the urinal  14 . An layer of thermochromic leuco dye  18  is applied to the surface  20  of the urinal mat  10 . Techniques for applying layers of thermochromic leuco dye onto substances that are impermeable to liquid are well known in the art. The urinal mat  10  is positioned over the drain  12  in the lower portion of the mouth  22  of the urinal  14  so that the urinal mat  10  is positioned to receive urine that is directed thereon by an individual. 
         [0014]    Referring to  FIG. 2A , the portion of the urinal mat  10  having the layer of thermochromic leuco dye  18  is shown. The temperature of the layer of thermochromic leuco dye  18  has not been raised by an outside source, and is shown applied on top of a message  24  that cannot be seen by an observer due to the layer of thermochromic leuco dye  18 , which is a color of the designer&#39;s choice. 
         [0015]    Referring to  FIG. 2B , the same portion of the urinal mat  10  is shown, but the temperature of the layer of thermochromic leuco dye  18  has been raised by an outside source  26  to reveal the message  24  that is printed underneath the layer of thermochromic leuco dye  18 . After the outside source  26  ceases to be applied to the layer of thermochromic leuco dye  18  to reveal the message  24  underneath, the temperature of the urinal mat  10  and layer of thermochromic leuco dye  18  will drop and the layer of thermochromic leuco dye will again conceal the message  24  from a viewer. 
         [0016]    Referring to  FIG. 3 , there is shown a standard urinal mat  28  as is commonly used in urinals such as the one depicted in  FIG. 1 . The urinal mat  28  comprises an enclosure  30  having baffles  32  that retain a deodorant cake  34 , wherein the enclosure  30  sits on a base  36 , and wherein the base  36  comprises a surface  38  upon which a message or image  40  is made with a layer  42  of thermochromic leuco dye covering the image  40 . The urinal mat  28  is made of a substance impermeable to liquid, such as plastic or rubber. As in the first embodiment shown in  FIGS. 1 ,  2 A, and  2 B, the layer  42  changes from color to an invisible or clear appearance upon the application of an outside heating source to reveal the message or image  40  below. 
         [0017]    Referring to  FIG. 4 , there is shown a standard toilet  44  having a device  46  for assisting in the toilet-training of young males. The device  46  comprises a hook  48  for attaching the device  46  to the ledge  50  of the toilet  44 , an arm  52 , and a surface  54  upon which a message or image is printed under a layer of thermochromic leuco dye. The device  46  is positioned such that the surface  54  is located at or near the waterline  56  inside the bowl  58  of the toilet  44 . The purpose of the device  46  is to provide a target for a young male to aim towards when learning to urinate inside a toilet. If the urine hits the surface  54  the temperature of the layer of thermochromic leuco dye will be raised and will become invisible so that the message or image underneath is revealed, allowing the young male to know that he has hit his target. 
         [0018]    Referring to  FIG. 5 , a dashboard  60  inside a motor vehicle is shown having a surface  62  wherein a message  64  is printed underneath a layer of thermochromic leuco dye. The layer of thermochromic leuco dye will change from a color to a clear or invisible appearance when it is heated, for example by the sun, revealing a message underneath that may be a warning to not leave children or animals unattended inside the vehicle. 
         [0019]    Although preferred embodiments of the invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions of parts and elements without departing from the spirit of the invention.