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

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/m2.

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/m2 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).

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.