| Abstract | U završnom radu ispitivana je brzina apsorpcije offsetne tiskarske boje u tiskovnu podlogu nakon otiskivanja. Brzina sušenja tiskarske boje vrlo je bitan čimbenik u tiskarskom procesu. Brzina apsorpcije predstavlja brzinu kojom tiskarska boja penetrira u tiskovnu podlogu nakon otiskivanja. Ona ovisi o upojnosti odabrane tiskovne podloge, tečljivosti tiskarske boje, brzini tiska te o doziranju boje na stroju. Ukoliko boja ne suši dovoljno brzo tada dolazi do sljepljivanja otisaka i stvaranja kontraotisaka.
U okviru rada ispitana je brzina apsorpcije jedne roto (cold-set) offsetne boje otisnute na dvije različite tiskovne podloge: novinskom papiru i magazinskom (LWC) papiru. Ispitivanje brzine apsorpcije provelo se u laboratorijskim uvjetima korištenjem standardiziranih IGT metoda i ureĎaja. Boja se tom prilikom tiskala na traku papira te se u odreĎenim vremenskim intervalima otisnuti papir prekrio čistim sjajno premazanim papirom na kojem se izradio kontraotisak. Brzina apsorpcije odredila se iz vrijednosti optičke gustoće dobivenih kontraotisaka denzitometrijskim mjerenjem. Kako bi se rezultati brzine apsorpcije tiskarske boje mogli bolje interpretirati, prije samog otiskivanja, na svakoj tiskovnoj podlozi, osim osnovnih svojstava (gramature, debljine i specifičnog volumena) odredila se i glatkost korištenih papira. TakoĎer se, prema IGT standardu W72 odredio prijenos tiskarske boje (g/m2) s tiskovne forme na svaku od korištenih tiskovnih podloga gravimetrijskom metodom. Na taj način se moglo utvrditi kolika je prijemčivost pojedinog papira za odabranu roto boju što u konačnici utječe i na brzinu apsorpcije navedene boje u pojedini papir.
Svi rezultati eksperimentalnog dijela prikazani su u tablicama, a na samom kraju doveden je zaključak o provedenom istraţivanju. |
| Abstract (english) | In this final thesis the absorption rate of offset printing ink was tested. Absorption is the speed with which ink penetrates into paper after printing. For the offset process this property is very important. It depends on the absorption ability of the selected printing substrate, ink flow and viscosity, the speed of the press and the dosage of the ink on the press. An absorption, which is, for example, too slow, may result in unwanted ink transfer in the form of set-off, smearing, or rub-off.
Fort the experiment conducted within this work two different printing substrates were used: standard newsprint paper and LWC (light weight coated) paper. Each paper was printed with same offset cold-set ink using an IGT A2 printability tester in standard laboratory conditions. After certain times the printed paper strip was brought into contact with a blank strip of a standard set off paper. Consequently, the part of the ink, which was still present at the surface of the printed strip, was transferred (smeared) on the set off strip. The absorption speed of the ink was evaluated from the density of the smeared ink on set off paper.
For better interpretation of obtained results, prior to printing, basis weight, thickness, and Bekk smoothness values were determined for both printing substrates. In addition, ink transfer expressed in g/m2 was calculated from the difference in weight of the printing form before and after printing and the size of the prints, as described in IGT Information leaflet W72. All obtained results were presented in tables and graphs, and a conclusion of conducted experiment was given at the end of this thesis. |
