Title
Dot gain analysis of round printing elements created by applying metalized foil using the cold-hot foil lamination process
Authors
IGOR MAJNARIĆ, MORIĆ MARKO, MATKO PINTAR and DAMIR MODRIĆ

Received September 25, 2024
Published Volume 58 Issue 9-10 September-December
Keywords half-tone metalized surface, UV Inkjet varnish, fine art paper, cold-hot lamination, dot gain

Abstract
The major objective of this paper consists in acquiring new knowledge and understanding the interaction between the printed metalized foil and the paper printing substrate. Since the Inkjet printing principle is often used for the adhesion of metalized foils (cold-hot process), it is necessary to investigate the influence of piezo Inkjet head settings on the final imprint. The light distribution on the halftoned metalized print depends on the optical properties of the paper and the metalized foil. Therefore, the problem of accurate reproduction is divided into the distribution of light in the paper and the reflection from the printed round metalized printing elements. For ImageJ software (gold dot imprint photographs), two physical quantities were analyzed (realized edge parts and anisotropic scattering of light from the printed surface = dot gain), which ultimately achieved a change in the realized dimension of print elements. In this paper, the authors present a new method for testing the efficiency of halftones (50% TV surface coverage) created with four diameters of gold foil printing dots (0.100 mm; 0.250 mm; 0.500 mm; 0.750 mm) applied to matte fine art cardboard. The experiment involved a gradual variation of the amount of UV-cured Inkjet varnish used, which played a crucial role in the production of metallic visual dot samples. To assess the effectiveness of this method, three different thicknesses of UV-cured varnish (29 µm, 43 µm, and 58 µm) were used in conjunction with modular Konica Minolta Jetvarnish 3DS machine (piezo Inkjet heads KM1024 iLHE-30), and constant printing speeds of 0.30 m/s. The research findings indicate that a 29 µm layer thickness of UV varnish and the substrate moving in cross-direction are optimal for producing cold metalized foil lines. However, the results also show that a more significant application of varnish offers a better chance of reproducing the dot and achieving a better contrast. The results show that elements smaller than 0.250 mm cannot be realized and that the print optimum will be achieved with UV Inkjet varnish application settings greater than 29 µm and less than 43 µm.