As the quality of printing equipment has progressed, closer tolerances were required in flexible printing plates used in connection with this equipment. Also as the speed of the printing equipment has increased, there has been a tendency of the plate cylinder carrying thwe printing plates to undesirably bounce as the leading edge of the printing plate engaged the impression or backup cylinder through the medium to be printed.
Because the close tolerances required by the printing equipment has been difficult to maintain in the printing plate molding and mounting operations, various attempts have been made to provide a printing plate which was able to provide compensation for a wider dimensional tolerance in the printing plate while maintaining good print quality and absorbing the high speed bounce affect. One such attempt has been to replace the standard double faced adhesive backing commonly known as "stickyback" with a sponge rubber cushion that had opposite sides coated with a pressure sensitive adhesive. While such attempt did produce the desirable tolerance compensation at the state of operation, several problems were encountered that has prevented the widespread use thereof.
One of these problems is that the cushioned material use did not have a resiliency such that the material fully recovered or rebounded between impressions on a printing machine thereby causing a compression set during operation to reduce the effectiveness of the cushion. Another problem is that it is difficult to obtain an adhesive which prevents lifting of the printing plate during operation. Yet another problem is that, because the strength of the cushion material is relatively weak, it is virtually impossible to remove it from the plate cylinder without destroying it once a printing run is completed. Even if the cushion material was destroyed upon removal, such removal is prohibitively time consuming and requires the use of strong solvents which may attack adjacent printing plates on the same printing cylinder. Another problem is that the solvents required for use in solvent base inks caused rapid deterioration of the cushion beyond usefulness.
USPTO Backgrounds
USPTO Backgrounds