Paper substrates incorporating covert marking pigments, and processes for obtaining and using same

Abstract

Paper substrates which incorporate covert marking pigments (CMPs) which are one or more infrared (IR) anti-Stokes pigments. Also, processes for incorporating such CMPs into a paper substrate other than by a printing technique, such as, for example, by using a size press or spraying, as well as processes for identifying the presence of such CMPs incorporated into a paper substrate sheet with an infrared (IR) pigment sensor of, for example, a copier or printer for the purpose of adjusting the quantity of printer pigment deposited on a paper substrate sheet or to determine whether the paper substrate sheet is an authentic or counterfeit document.

What is claimed is: 
     
         1 . A covertly marked paper substrate article comprising:
 a paper substrate; and   a covert marking pigment having a particle size in the range of from about 0.1 to about 5 microns and being incorporated into the paper substrate in an IR detectable amount of from about 0.1 to about 1,000 mg/m 2 , the covert marking pigment being one or more IR anti-Stokes shift pigments selected from one or more of: yttrium oxide; sodium yttrium fluoride; lanthanum oxide; lanthanum fluoride; yttrium oxysulfide; lanthanum oxysulfide; Gadolinium (Gd2O2S); Ytterbium (Yb); or mixtures thereof.   
     
     
         2 . The article of  claim 1 , wherein the covert marking pigment has a particle size in the range of from about 0.5 to about 1.5 microns. 
     
     
         3 . The article of  claim 1 , wherein the covert marking pigment is incorporated into the paper substrate in an IR detectable amount of from about 2 to about 10 mg/m 2 . 
     
     
         4 . The article of  claim 1 , wherein the IR anti-Stokes shift pigments are selected from one or more of: yttrium oxide; sodium yttrium fluoride; lanthanum oxide; Gadolinium (Gd2O2S); or Ytterbium (Yb). 
     
     
         5 . The article of  claim 1 , wherein the covert marking pigment is distributed randomly in the paper substrate. 
     
     
         6 . The article of  claim 1 , wherein the paper substrate has two outer surfaces and wherein the covert marking pigment is applied to one of the two outer surfaces. 
     
     
         7 . The article of  claim 1 , wherein the paper substrate has two outer surfaces and wherein the covert marking pigment is incorporated below the two outer surfaces. 
     
     
         8 . The article of  claim 1 , which is in the form of a ream of paper substrate sheets, at least a portion of the ream comprising covertly marked paper substrate sheets. 
     
     
         9 . The article of  claim 8 , wherein the covertly marked paper substrate sheets in the ream comprise from one in three to from one in five paper substrate sheets in the ream. 
     
     
         10 . The article of  claim 8 , wherein the paper substrate sheets have two opposed side edges, and wherein the covert marking pigment is incorporated on one of the side edges of each covertly marked paper substrate sheet in the ream. 
     
     
         11 . The article of  claim 1 , wherein the paper substrate includes an optical brightening agent. 
     
     
         12 . A process for preparing a covertly marked paper substrate, the process comprising the following steps:
 (a) providing a composition having a covert marking pigment having a particle size in the range of from about 0.1 to about 5 microns, the covert marking pigment being one or more IR anti-Stokes shift pigments selected from one or more of: yttrium oxide; sodium yttrium fluoride; lanthanum oxide; lanthanum fluoride; yttrium oxysulfide; lanthanum oxysulfide; Gadolinium (Gd2O2S); Ytterbium (Yb); or mixtures thereof; and   (b) incorporating the composition of step (a) by a non-printing technique into a paper substrate in an IR detectable amount of from about 0.1 to about 1,000 mg/m 2 .   
     
     
         13 . The process of  claim 12 , wherein the composition of step (a) comprises a size press composition which further comprises a sizing agent, and wherein the size press composition is incorporated into the paper substrate in step (b) at a size press. 
     
     
         14 . The process of  claim 12 , wherein the covert marking pigment of step (a) has a particle size in the range of from about 0.5 to about 1.5 microns. 
     
     
         15 . The process of  claim 12 , wherein the covert marking pigment is incorporated into the paper substrate during step (b) in an IR detectable amount of from about 2 to about 10 mg/m 2 . 
     
     
         16 . The process of  claim 12 , wherein the IR anti-Stokes shift pigments of step (a) are selected from one or more of: yttrium oxide; sodium yttrium fluoride; lanthanum oxide; Gadolinium (Gd2O2S); or Ytterbium (Yb). 
     
     
         17 . The process of  claim 12 , wherein step (b) is carried out by randomly distributing the covert marking pigment in the paper substrate. 
     
     
         18 . The process of  claim 12 , wherein the paper substrate of step (b) has two outer surfaces and wherein the covert marking pigment is applied to one of the two outer surfaces during step (b). 
     
     
         19 . The process of  claim 12 , wherein the paper substrate of step (b) is formed into a ream of paper substrate sheets, and wherein from one in three to from one in five paper substrate sheets in the ream are covertly marked paper substrate sheets. 
     
     
         20 . The process of  claim 19 , wherein the paper substrate of step (b) has two opposed side edges, and wherein the covert marking pigment is incorporated on one of the side edges of each covertly marked paper substrate sheet in the ream. 
     
     
         21 . A process for adjusting the amount of printer pigment deposited on a paper substrate sheet, the process comprising the following steps:
 (a) providing a covertly marked paper substrate sheet, the covertly marked paper substrate sheet comprising:
 a paper substrate sheet; and 
 a covert marking pigment having a particle size in the range of from about 0.1 to about 5 microns and being incorporated into the paper substrate sheet in an IR detectable amount of from about 0.1 to about 1,000 mg/m 2  and in a manner which identifies a type of covertly marked paper substrate sheet, the covert marking pigment being one or more IR anti-Stokes shift pigments selected from one or more of: yttrium oxide; sodium yttrium fluoride; lanthanum oxide; lanthanum fluoride; yttrium oxysulfide; lanthanum oxysulfide; Gadolinium (Gd2O2S); Ytterbium (Yb); or mixtures thereof; and 
   (b) scanning a paper substrate sheet with an IR pigment sensor to adjust the quantity of printer pigment deposited on the covertly marked paper substrate sheet in response to identify the type of covertly marked paper substrate sheet; and   (c) adjusting the quantity of printer pigment deposited on the covertly marked paper substrate sheet in response to the type of covertly marked paper substrate sheet identified in step (b).   
     
     
         22 . The process of  claim 21 , wherein the paper substrate sheet of step (a) has two outer surfaces and wherein the covert marking pigment is applied to one of the two outer surfaces, and wherein the IR pigment sensor of step (b) scans the outer surfaces of each of the paper substrate sheets of step (a). 
     
     
         23 . The process of  claim 21 , wherein each paper substrate sheet of step (a) has two opposed side edges, and wherein the covert marking pigment is applied to one of the two side edges of each covertly marked paper substrate sheet, and wherein the IR pigment sensor of step (b) scans the side edges of each of the paper substrate sheets of step (a). 
     
     
         24 . The process of  claim 21 , wherein the covert marking pigment incorporated into the paper substrate sheets of step (a) has a particle size in range of from about 0.5 to about 1.5 microns and is in an IR detectable amount of from about 2 to about 10 mg/m 2 . 
     
     
         25 . The process of  claim 21 , wherein the IR anti-Stokes shift pigments of step (a) are selected from one or more of: yttrium oxide; sodium yttrium fluoride; lanthanum oxide; Gadolinium (Gd2O2S); or Ytterbium (Yb). 
     
     
         26 . The process of  claim 21 , wherein the covert marking pigment is distributed randomly in the paper substrate sheets of step (a). 
     
     
         27 . The process of  claim 21 , wherein the paper substrate sheets of step (a) are formed into a ream of paper substrate sheets, and wherein from one in three to from one in five paper substrate sheets in the ream are covertly marked paper substrate sheets. 
     
     
         28 . A process for determining whether or not a paper substrate sheet is an authentic document, the process comprising the following steps:
 (a) providing a paper substrate sheet; and   (b) scanning the paper substrate sheet with an IR pigment sensor to detect whether the paper substrate sheet incorporates a specified covert marking pigment, the covert marking pigment being one or more IR anti-Stokes shift pigments selected from one or more of: yttrium oxide; sodium yttrium fluoride; lanthanum oxide; lanthanum fluoride; yttrium oxysulfide; lanthanum oxysulfide; Gadolinium (Gd2O2S); Ytterbium (Yb); or mixtures thereof;
 wherein if the IR pigment sensor detects that the paper substrate sheet: (i) does incorporate the specified covert marking pigment, the paper substrate sheet is identified as authentic; or (ii) does not incorporate the specified covert marking pigment, the paper substrate sheet is identified as counterfeit. 
   
     
     
         29 . The process of  claim 28 , wherein each paper substrate sheet of step (a) has two outer surfaces, and wherein each paper substrate sheet which is an authentic document incorporates the specified covert marking pigment into the paper substrate sheet below the two outer surfaces. 
     
     
         30 . The process of  claim 28 , wherein the covert marking pigment is distributed randomly in the paper substrate sheets of step (a). 
     
     
         31 . The process of  claim 28 , wherein the IR anti-Stokes shift pigments of step (a) are selected from one or more of: yttrium oxide; sodium yttrium fluoride; lanthanum oxide; Gadolinium (Gd2O2S); or Ytterbium (Yb).