Influence of UV curing varnish coating on surface properties of paper

U svrhu postizanja boljih svojstava tiskovne je podloge moguće oplemenjivati na različite načine. U ovom radu analizira se mogućnost oplemenjivanja s različitom površinskom pokrivenošću lakova koji se suše UV zračenjem, pri čemu su korištena tri karakteristična papira (papir za umjetnički tisak gloss, offsetni papir i kalandriran papir). Primijenjene metode su bazirane na mjerenju optičkih svojstava lakom impregnirane površine (obojenje, sjaj i glatkoća), kao i na određivanju fizikalnog svojstva upojnosti. Dvojne osobine papirnih podloga dobivaju se nanosom UV laka koji suši LED svjetlošću. Rezultati istraživanja pokazuju da se kod gloss premazanog papira upojnost smanjuje nanosom UV laka, dok se kod nepremazanih papira (offsetni, kalandrirani) upojnost povećava. Nanos laka s manjom površinskom pokrivenošću (33 % UV laka) nije relevantntna za upojnost i optička svojstva naravnih papira. Značajne promjene u hrapavosti i optičkim svojstava postižu se 66 % nanosom, što je posebice vidljivo kod papira za umjetnički tisak.In order to achieve better properties of the printing substrates their improving is possible in various ways. In this article the possibility of the substrate improving is analyzed with different surface coverage of varnishes cured by UV radiation, where three characteristic kinds of paper were used (fine art glossy paper, offset paper and calendered paper). The applied methods are based on measuring the optical properties with the varnish impregnated surface (colouring, gloss, smoothness), as well as determining the physical property of absorbency. Double properties of the printing substrates are obtained by the layer of UV varnish which is cured by LED light. The investigation results show that the absorbency decreases on gloss coated paper by the application of UV varnish coating, while it increases on uncoated paper (offset and calendered paper). The varnish coating with smaller coverage (33 % UV varnish) is not relevant for the absorbency and for optical properties of the natural paper. Important changes in roughness and optical properties are achieved with 66 % coating which is especially visible on fine art paper