STABILITY OF UV CURABLE INKS APPLIED IN THREE LAYERS ON PAPERS CONTAINING STRAW PULP AFTER ARTIFICIAL AGEING

In order for prints to be considered high quality, regardless of the type of printing substrate, they must retain the initial optical quality achieved during printing and years after the printed product has been used or stored. The rate at which print quality deteriorates over time depends on several factors. The composition of the printing substrate, the composition of the printing ink, the technique of applying the ink to the substrate, and the interaction between the ink and the substrate have the greatest influence on the initial quality. In addition to the listed influences on the durability of the print quality, the conditions under which the print was used or stored, such as humidity, temperature, microorganisms, and air quality, also have an effect. Paper is the most commonly used printing substrate, and considering the favourable ecological components of this material, it will be used more and more in the future. The need for alternative raw materials to wood in its production will also become more pronounced. Precisely because of the cellulose fibres that make up its basis, paper is subject to many degradation changes. In this research, the optical and colorimetric stability of prints on paper with straw pulp from different cereals were monitored after two cycles of accelerated ageing of 48 hours, performed according to the ASTM D 6789-02 standard. As the stability of prints in which UV curable inks were applied in three layers on laboratory paper by screen and gravure printing techniques was monitored in parallel, it was determined that screen prints have better colorimetric stability compared to gravure prints. It was also observed that for both types of inks, the most significant degradation occurs in the first 48 hours of accelerated ageing, while further prolonging the exposure time of the prints irradiance through the daylight filter does not show any significant continuation of the degradation.