System for and method of producing a security mark on a micro-porous stucture

Abstract

A security mark is produced on a micro-porous, synthetic paper, structure by changing light transmission properties of light pathways through the structure. The security mark is visible when the structure is illuminated.

1 . A method of producing a security mark on a micro-porous structure to be secured, comprising:
 forming selected portions of the micro-porous structure in a pattern corresponding to the security mark to be produced; and   changing light transmission characteristics of the selected portions to transmit light through the selected portions at different light levels to render the security mark visible when the micro-porous structure is illuminated.   
     
     
         2 . The method of  claim 1 , wherein the forming is performed by scanning a laser beam relative to the micro-porous structure in the pattern, and wherein the changing is performed by ablating the selected portions to different thicknesses corresponding to the different light levels. 
     
     
         3 . The method of  claim 2 , wherein the ablating is performed by removing outer layers of the selected portions from an outer surface of the micro-porous structure. 
     
     
         4 . The method of  claim 1 , wherein the forming is performed by scanning radiant energy relative to the micro-porous structure in the pattern, and wherein the changing is performed by distorting pores of the micro-porous structure at the selected portions to different sizes and shapes corresponding to the different light levels. 
     
     
         5 . The method of  claim 1 , wherein the forming is performed by forming a die in the shape of the pattern, and wherein the changing is performed by heating the die, and pressing the heated die into contact with the micro-porous structure until pores of the micro-porous structure at the selected portions are distorted to different sizes and shapes corresponding to the different light levels. 
     
     
         6 . The method of  claim 1 , and configuring the micro-porous structure as a polymeric sheet containing a multitude of pores that constitutes at least 50% by volume of the micro-porous structure, and wherein the sheet has opposite major surfaces through at least one of which the illumination light passes to render the security mark visible. 
     
     
         7 . A system for producing a security mark on a micro-porous structure to be secured, comprising:
 means for forming selected portions of the micro-porous structure in a pattern corresponding to the security mark to be produced; and   means for changing light transmission characteristics of the selected portions to transmit light through the selected portions at different light levels to render the security mark visible when the micro-porous structure is illuminated.   
     
     
         8 . The system of  claim 7 , wherein the changing means includes a laser for emitting a laser beam operative for ablating the selected portions to different thicknesses corresponding to the different light levels, and wherein the forming means includes a controller for scanning the laser beam relative to the micro-porous structure in the pattern. 
     
     
         9 . The system of  claim 8 , wherein the laser beam is operative for removing outer layers of the selected portions from an outer surface of the micro-porous structure. 
     
     
         10 . The system of  claim 7 , wherein the changing means includes a radiant energy source for emitting radiant energy operative for distorting pores of the micro-porous structure at the selected portions to different sizes and shapes corresponding to the different light levels, and wherein the forming means includes a controller for scanning the radiant energy relative to the micro-porous structure in the pattern. 
     
     
         11 . The system of  claim 7 , wherein the forming means is a die in the shape of the pattern, and wherein the changing means is operative for heating the die, and for pressing the heated die into contact with the micro-porous structure until pores of the micro-porous structure at the selected portions are distorted to different sizes and shapes corresponding to the different light levels. 
     
     
         12 . The system of  claim 7 , wherein the micro-porous structure is a polymeric sheet containing a multitude of pores that constitutes at least 50 percent by volume of the micro-porous structure, and wherein the sheet has opposite major surfaces through at least one of which the illumination light passes to render the security mark visible. 
     
     
         13 . A secured document, comprising:
 a micro-porous structure configured as a polymeric sheet having opposite major surfaces and containing a multitude of pores that constitutes at least 50 percent by volume of the micro-porous structure,   selected portions of the micro-porous structure being arranged in a pattern corresponding to a security mark to secure the document, and   the selected portions having changed light transmission characteristics to transmit light through the selected portions at different light levels to render the security mark visible when the micro-porous structure is illuminated from at least one of the major surfaces.   
     
     
         14 . The secured document of  claim 13 , wherein the micro-porous structure is a Teslin® substrate. 
     
     
         15 . The secured document of  claim 13 , wherein the selected portions are of different thicknesses. 
     
     
         16 . The secured document of  claim 13 , wherein the pores at the selected portions have different sizes and shapes.