Patent ID: 6314879
Filing Date: 2001-11-13
Classification: B41F,Y10S

Abstract:
A flexographic printing apparatus for printing a moving web, said printing apparatus comprising:a rotatable ink roller;a roller support that rotatably supports said ink roller;an ink source associated with said ink roller, said ink source providing ink to be applied to said ink roller;a rotatable printing roller associated with said ink roller;a printing plate disposed on said printing roller, said printing plate being supported so that ink is transferred from said ink roller to said printing plate as said ink roller and said printing roller rotate, said printing plate comprising:a semi-conductive printing layer having an image-forming surface, said semi-conductive printing layer comprising a photo-sensitive polymer material; anda substrate layer on which said semi-conductive printing layer is formed, said substrate layer comprising an insulating material having a resistivity of greater than about two megohms per cubic centimeter,said semi-conductive printing layer comprising a plurality of portions of semi-conductive material formed on said substrate layer, said portions of said semi-conductive material being spaced apart and formed so that portions of said substrate layer are not covered by said portions of said semi-conductive material;a first insulating layer disposed on said printing roller, said first insulating layer being disposed between an outer surface of said printing roller and said printing plate;a second insulating layer disposed on said printing roller, said second insulating layer being disposed between said outer surface of said printing roller and said first insulating layer;a rotatable backing roller disposed adjacent said printing roller so that said moving web to which ink is to be applied passes between said backing roller and said printing plate as said backing roller and said printing roller rotate so that a printed image is applied to said web; anda charge applicator associated with said printing roller, said charge applicator causing an electric charge to be applied to said printing plate, said charge applicator comprising an elongate charge bar having a plurality of charging electrodes spaced from said printing plate, said charging electrodes being evenly spaced from each other in a direction parallel to a central axis of said printing roller, each of said charging electrodes being conductively connected to a voltage.