CHANGES IN VISUAL APPEARANCE OF RED AND GREEN UV-VISIBLE FLUORESCENT PRINTS AS A CONSEQUENCE OF THE ACCELERATED AGEING

Lora Stengl; Tamara TOMAŠEGOVIC

Authors

Lora Stengl University of Zagreb
Tamara TOMAŠEGOVIC University of Zagreb

Keywords:

screen printing, UV- visible fluorescent pigments, artificial ageing, visual appearance

Abstract

Pigments with special effects are nowadays utilized in the graphic engineering and design to achieve an added value of the final product. Daylight-invisible, UV-visible fluorescent pigments can be used as markings, sensors, as well as special design or security feature. Red and green UV-visible fluorescent pigments used in this experiment were mixed in the transparent base and screen-printed using the 60 l/cm mesh on the white uncoated paper, by applying different number of printed ink layers: one, two and three. Prints were then subjected to the accelerated ageing in a weathering chamber. Ink layer thickness and colorimetric properties of the unaged and aged prints were analyzed. Microscopic and macroscopic images of the prints were taken before and after the ageing process do assess the subjective visual difference between the unaged and aged samples. Results of this research have shown that one printed layer of the ink had inadequate visual response of fluorescence because of the effect of the optical brighteners in the paper. Higher number of the ink layers on print displayed better fluorescence effect and improved light fastness compared to the print obtained by applying only one ink layer. Results of the colorimetric measurements, as well as microscopic and macroscopic images, displayed the objective and subjective differences in the color appearance of the unaged and aged prints. Thereby, results of this research provided

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