269 ANALYSIS OF COLUOR REPRODUCTION CREATED BY APPLYING MULTIPLE LAYERS OF WHITE INK ON PVC FOIL Majnarić Igor, Golubović Kristijan, Bolanča Stanislav, Modrić Damir University of Zagreb, Faculty of Graphic Arts, Getaldićeva 2, 10 000 Zagreb Sažetak: Direktno nanašanje pigmentiranih procesnih bojila (CMYK) na prozirne tiskovne podloge (PVC, polikarbonat, staklo) neće dati zadovoljavajuću kolornu vrijednost. U odnosu na refleksijske tiskovne podloge (papir, karton, metal, koža…), prozirni tiskarski materijali će zbog svoje visoke transparencije izgledati blijedo i slabo uočljivo. Rješenje tog problema je u dodatnom otiskivanju bijelog bojila koje će poslužiti kao podložna maska, sve u cilju smanjenja trasparencije. U ovom radu napravljena je kolorimetrijska analiza utjecaja različitog broja nanosa bijelog bojila (bojilo je pigmentirano sa TiO 2 ) na kolornu reprodukciju. Pritom će se konstruirati gamuti koji predstavljaju krajnji tonski opseg. Stvarna promjena karakterističnih tonova (CMYK) dobivena je izračunom razlike u obojenju (CIE LAB ∆E 2000 ) koja će direktno pokazati utjecaj apliciranja bijelog bojila na kolornu reprodukciju transparentnih grafičkih proizvoda. Međusobna ovisnost opaciteta o broju otisnutih slojeva opisana je logaritamskom funkcijom. Cilj ovog rada je da se osim devijacije tonskih vrijednosti, pokuša ustanoviti i optimalni broj apliciranih bijelih slojeva. Time će se otisak približiti referenci (otisku na papiru za umjetnički tisak otisnutom u istoj tehnici) uz ekonomski prihvatljive troškove otiskivanja. Ključne riječi: Ink Jet, gamut, PVC tiskovna podloga, tisak bijele boje Abstract: Direct application of the pigmented process inks (CMYK) on transparent printing foils (PVC, polycarbonate, glass) does not give the satisfactory colour value. In regard to the reflective printing substrates (paper, board, metal, leather…), the prints on transparent printing materials look pale and not noticeable enough because of their high transparency. The solution of this problem is the additional printing with white ink which serves as the under mask with the aim to reduce the transparency. The colorimetric analysis of the influence of different number of white ink layers (the ink was pigmented with TiO 2 ) on the colour reproduction was done in this paper. The gamuts were constructed which represented the final tonal range. The real change of the characteristic tones (CMYK) was obtained by calculation of inking difference (CIE LAB ∆E 2000 ) which directly showed the influence of application of the white ink on the colour quality of the transparent printed products. The mutual dependence of opacity and the number of the printed layers was described by the logarithmic function. The aim of this work is except the deviations of the tonal values, to find the optimal number of the applied white layers. In this way the print nears the referent value (print on fine art paper printed with the process colour inks) with the economically acceptable printing costs. Key words: DoD Ink Jet, gamut, PVC printing substrate, increasing layer of white ink