Utjecaj nekih karakteristika papirne podloge na UV stabilnost sitotiskarskih termokromnih otisaka

Influence of paper substrate characteristics on UV stability of screen-printing thermochromic prints

Rahela Kulčar, Melita Petrić, Marina Vukoje

Sveučilište u Zagrebu Grafički fakultet

Sažetak

Problematika primjene termokromnih tiskarskih boja uvelike je vezana uz njihovu UV stabilnost. Duža izloženost UV zračenju utječe na funkcionalnost termokromnih boja tj. na njihovu glavnu karakteristiku, a to je promjena boje na određenoj temperaturi aktivacije. Neka ispitivanja koja su provedena na termokromnim bojama pokazala su da na njihovu postojanost može utjecati i sam materijal na koji se otiskuje. Cilj rada je ispitati mogućnost utjecaja nekih karakteristika papira na stabilnost termokromnih otisaka s naglaskom na prisutnost optičkih bjelila u papiru. U ispitivanje su uključene dvije različite vrste papira, različitih karakteristika na koje je otisnuta UV sušeća sitotiskarska termokromna boja. Otisci su podvrgnuti procesu ubrzanog starenja u komori za starenje, a utjecaj UV zračenja na stabilnost otisaka praćen je kolorimetrijskim mjerenjem uzoraka kroz proces zagrijavanja i hlađenja kako bi se utvrdila postojanost otisaka i trajanje efekta promjene boje.
Ključne riječi: termokromne boje, optička bjelila, UV stabilnost, ubrzano starenje

Abstract

Application issues of thermochromic ink is largely related to its UV stability. Longer exposure to UV radiation affects the functionality of thermochromic inks, i.e. their main characteristic, which is the change of color at a certain activation temperature. Some studies performed on thermochromic inks have shown that their durability can be affected by the substrate used for printing. The aim of this paper is to examine the possibility of the influence of some characteristics of paper on the stability of thermochromic ink with the emphasis on the presence of optical brighteners in the paper. Two different types of paper, with different characteristics, on which the UV curable screen-printing thermochromic ink was printed, were included in the test. The prints were exposed to an accelerated aging process in an aging chamber, while the influence of UV irradiation on the stability of the prints was monitored by the colorimetric measurement of the samples through a heating/cooling process to determine their durability and the duration of the color change effect.
Key words: thermochromic inks, optical brighteners, UV stability, accelerated aging

rahela.kulcar@grf.unizg.hr