Plastic films or sheets having tear lines formed therein are disclosed. These films are made by forming a score along a predetermined line in the surface of a plastic film to form a tear line and then restoring the scored film surface without eliminating the line of tear. The products tear very easily...http://www.google.de/patents/US4217327?utm_source=gb-gplus-sharePatent US4217327 - Method of forming tear lines in plastic films
