Marking paper products

Abstract

Methods of marking paper products and marked paper products are provided. Some methods include irradiating the paper product to alter the functionalization of the paper.

What is claimed is: 
     
         1 . A marked paper product comprising:
 a sheet comprising a cellulosic material in a plastic matrix,   wherein an irradiated discrete, predefined portion of a surface of the sheet contains functional groups or a number thereof not present in the sheet prior to irradiation or in a non-irradiated portion of the cellulosic material of the same surface of the sheet, and   wherein the functional groups not present in the sheet prior to irradiation are formed by irradiation of the discrete, predefined portion with accelerated particles.   
     
     
         2 . The marked paper product of  claim 1  wherein the discrete portion of the sheet comprises a number of carboxylic acid groups that is greater than is present in the sheet prior to irradiation or in the non-irradiated portion of the cellulosic or lignocellulosic fibrous material. 
     
     
         3 . The marked paper product of  claim 1  wherein the functional groups are selected from the group consisting of aldehyde groups, nitroso groups, nitrile groups, nitro groups, ketone groups, amino groups, alkyl amino groups, alkyl groups, chloroalkyl groups, chlorofluoroalkyl groups, and enol groups. 
     
     
         4 . The marked paper product of  claim 1  wherein the marked paper product comprises a note. 
     
     
         5 . The marked paper product of  claim 4  wherein the marked paper product is a paper-comprising currency. 
     
     
         6 . The marked paper product of  claim 5  wherein the currency is paper money. 
     
     
         7 . The marked paper product of  claim 1  wherein the predefined portion is in the form of a symbol. 
     
     
         8 . The marked paper product of claim  10  wherein the predefined portion is in the form of a watermark.