Lightfastness of lithographic primary colours coated with nanocomposites composed of tio2 and water-based varnish

Abstract

The UV radiation causes inks to fade. The ink fading will lead to the degradation of the visual appearance of printed imprints making them less attractive to the user. To deal with this that phenomenon, one of the solutions is to create a coating that could challenge these issues. In order to create efficient protective coating against UV induced degradation, nano scaled titanium dioxide (TiO2) wasl added to the commercial water-based varnish. To determine influence of the amount of TiO2, was homogenized in various weight ratios. The prepared nanocomposites were applied onto offset (lithography) prints made in accordance with Fogra PSO, i.e. ISO 12647-2:2013 on gloss coated paperboard. The samples have been subjected to artificial UV induced aging for 30 hours. The protective properties of the nanocomposite TiO2 coating was determined by calculating colorimetric and densitometric change on full tone and determining tone value change of half tones. The results showed that the prepared nanocomposite coating has relatively little effect on the printed colour of the samples. However, some coating compositions exceed the allowed tolerance ΔEab> 5, however in those cases the initial colorimetric value of WB (ΔEab) was close to the FOGRA PSO border value. The coatings with TiO2 will increase resistance to accelerated ageing on full and halftone. To conclude, this research has provided the new perspective on modulation possibilities of commercially available varnishes in order to cope a designated problematics and downsides of coatings which was, in this case, UV induced fading and degradation of visual appearance. The further research should investigate the applicability of this kind of modulated varnish in other coating techniques as well the use of other kind of nano sized compounds.