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The Influence of NOx on the Stability of the White Colored Inkjet Prints

Printing on the dark (black colored) and transparent substrates is impossible without the application of white inks. In this case, the high covering inorganic pigments based on titanium dioxide are used. Although the printing of the white ink can be used in conventional printing techniques (flexographic printing, gravure printing and offset printing), it is more frequently used in Inkjet UV curing technology. Unfortunately, the concentration of the white pigments cannot be modified in Inkjet. Therefore, the optimal color values were printed in three layers on black substrate, using white UV LED curing Inkjet ink. Since the stability of white Inkjet prints is still unknown, the accelerated ageing method at higher temperature and increased concentration of NOx (ISO 5630-5, 6) was used. The results showed great influence of NOx on white UV LED Inkjet colorants. Major color changes occurred after the first day of exposure of the prints to NOx (∆E2layers, 1st day of exposure to NOx, 100%HV=42, 72). No significant color changes happened afterwards (∆E2layers, 5th day of exposure to NOx, 100%HV=42, 89).

Accelerated ageing with NOx; white UV LED Inkjet inks; multilayer printing; CIE LAB DE

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