Evalution of plate performance on UV flexographic ink transfer

Abstract

Photopolymer plates are expected to produce good area coverage with low dot gain, fine reverses and light halftones. However, the obtained print results often differ depending on plate system used such as type of photopolymer plate, cushion materials and double-sided tape. Thus, the choice of the particular elements used have an impact on the plate system performance, which relevant to dot gain and ink transfer. To determine the performance of the plate system in detail, we need to know plate properties such as surface hardness, elasticity, surface energy including its caliper, the pressure absorbency characteristics of the cushion and the press setting. Thus, a number of checking procedures are introduced to define the effects of the plate system's performance on printing quality. This includes checking material specifications, and the condition of press such as register, anilox roller, doctor blade system and press setting. Experimental design for adhesive label UV flexographic printing thus was proposed and printed jobs had been evaluated. The amount of ink transfer has been measured and the ink transfer model has been established. Then the ink transfer has been analyzing and compare to printed quality of print targets and stepwedges. The results showed that the total amount of ink transfer affected tone gradation, print uniformity, fine reverse and dot gain. While better ink transfer from plate to substrate could affect towards darker edge of fonts of the reverse print, good print uniformity and less gradation. Note that the total dotgain results showed complexity as there were other factors involved such as surface energy, compressibility and surface hardness of printing plate too.