WATERMARKING BY INK SET PRINTING

摘要

An unobtrusive image is applied to paper or other sheet material by means of a charged droplet printer, for example an ink jet printer. The unobtrusive image applied may perform the function usually associated with a watermark in paper, but in contrast to a watermark, may be applied to papers during their production on high speed wide deckle machines or to coated papers. The method is particularly suitable for unobtrusively imaging pressure sensitive copying material.