UV Processing of Digital Printing

Abstract

UV (ultraviolet) curing is the process of photoinitiated conversion of polymeric materials from a liquid to a solid. It has become a popular alternative to conventional drying in a large number of printing and coating applications. The development of new UV-curable inks, and effective use of lamps systems, creates new opportunities to increase cure efficiency, speed, and the physical properties of the cured polymer film.UV Curing is highly adaptable to printing, coating, decorating and assembling of a great variety of products and materials owing to some of its key attributes; it is:• a solventless process–cure is by polymerization rather than by evaporation, so VOC emissions are eliminated;• a low temperature process–heat is not required;• a high speed process–cure is nearly instantaneous;• an energy-efficient process–energy is invested only in the curing reaction, not in heating;• easily controlled–inks and coatings do not “dry,” so do not set up in printing/coating equipment.UV-curable systems have recently succeeded in a large number of new applications, and replaced conventional solvent-based inks and drying in established processes. The effectiveness of a UV curing system is the practical result of a process design which combines the method of application of ink or coating, the photochemistry of UV-curable inks, and the UV lamp designs into an integrated system. Careful attention to the optical factors and the interaction of inks and lamps can provide a successful UV system with wide operating limits. New developments in digital printing make UV processing an attractive technology for drying.