Flexographic printing begins with development of a flexographic plate. Flexographic plates can be created using three different methods. One method uses a UV reactive polymer . UV light is shined onto a film negative positioned over the polymer. The polymer reacts to the UV that comes through the negative and hardens. The unhardened polymer is removed using water or a chemical solvent.
A second technique is digital platemaking. Digital platemaking involves establishing the wanted image in a digital format (typically with a desktop publishing program) and using that digital master image to laser-etch the plate.
The final method is to create a mold. In this technique, a photoreactive, metal plate is exposed using a negative. Following the exposure, the photoreactive plate is given an acid bath creating an engraved image. A master plate mold is produced from the engraved metal plate, and the final printing plate is produced from the master mold.
There are a number of different types of flexographic printers, usually set up to accommodate special printing needs. The basic principles employed tend to be the same from printer to printer. Effectively, there are three rollers involved: a meter roll (so called because it meters the amount of ink applied to the plate), a roller with the plate attached, and a impression roller. The meter roll applies a predetermined measurement of ink to the plate. The plate is subsequently scraped by the doctor blade. The substrate (the material to be printed on) is passed between the print plate and the impression roller, which applies pressure to the keep the substrate against the plate.
Flexographic printing can be performed on a wide range of materials. Historically, it has been used to print on cardboard and food packages. Today, virtually any type of substrate can be used in flexographic printing. Some of the more popular materials are plastic, paper, cardboard (still) and cellophane. It remains widely used in newspaper, catalog, label and packaging printing .