Fotopolymerplater

Fotopolymerplater, or photopolymer plates, are light-sensitive printing plates used to create relief images for letterpress and other forms of relief printing such as flexography. They are applied on flexible bases, typically polyester, and come in various thicknesses to suit different presses. Photopolymer plates enable rapid plate making from digital files and are commonly used for short to medium print runs, packaging, labels, and custom stationery.

The plates consist of a transparent substrate coated with a photosensitive polymer. When the plate is exposed to ultraviolet light through a film or digital mask, the exposed areas polymerize and become resistant to the development fluid. The unexposed areas are washed away, leaving a raised relief that can be inked and transferred to paper or other substrates. Some plates use water-based developers, while others require solvent-based developers. After development, a post-exposure step hardens the surface to improve durability for printing.

Production process. A digital artwork is prepared and can be exposed directly by a plate imaging device or via a film-positive. The plate is exposed to UV light to harden the image areas, developed to remove unexposed resin, rinsed and dried, and then post-exposed to increase hardening before mounting on a press. The resulting relief carries ink and transfers it to the substrate during printing.

Advantages and limitations. Photopolymer plates offer fast turnaround, high image resolution, and suitability for short runs with complex graphics, while avoiding metal etching. They integrate well with digital workflows. Limitations include wear resistance inferior to metal for very long runs, sensitivity to storage and processing conditions, and environmental considerations related to washout chemicals and plate disposal.

Variants and processing. There are water-wash plates that minimize solvent use and solvent-developable plates with different durability profiles. Plate thickness and relief height are chosen based on printing method and ink requirements.