Erase-Proof Thermal Inks
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-04
The addition of a natural wax or polyethylene to a thermoplastic resin ink system lowers the melt viscosity so that the ink flows into paper and cannot be cleanly erased. Thermoplastic resins used in printing are selected to be smudge-resistant and not to stick to an adjoining surface when rolled in a spool (often termed blocking). Such resins, especially those deposited from water-borne or latex emulsions, only flow to the paper surface and can be erased by abrasion or adhesive lift-off without leaving a noticeable trace when such resins are the only body of the ink. To achieve erase-proof inks, enough wax or polyethylene is added to a standard thermoplastic-resin ink system to prevent easy erasure, but not so much as to cause problems with pressure sensitivity, color bleeding in the print, and blocking in the ribbon spool.