Decreasing metamerism of inkjet printed wood grain

Abstract

Today, the competitive environment in the graphics communication industry is demanding the printer to produce good quality products within short periods of time. To ensure quality reproduction of print jobs, prototyping is necessary. Rotogravure cannot be used for prototyping, because of high manufacturing cost of gravure cylinders. Such challenges can be successfully tackled by use of relatively cheap and flexible printing processes, such as inkjet. Even though inkjet printing is a cost-effective way for prototyping, it has its own limitations, especially in the case of wood grain printing. Wood grain patterns need to be printed with a release coating and adhesive. Inkjet printers are incapable of printing either release coating or adhesive, because they require a certain amount of coat weight, not possible to deliver with inkjet printing. Inaccurate color reproduction, metamerism and incompatibility with release coat are the commonly seen problems during inkjet prototyping. The main aim of this study was to resolve problems such as metamerism and close color match of inkjet and gravure printed wood grain. A design of experiments (DOE) was carried out by using different factors such as gray component replacement (GCR) settings, release coat weight and use of tie coat to analyze their effect on metamerism. Custom created ICC profiles decreased the metamerism index (MI) and ∆E*_ab significantly, when compared with the generic RIP printer profile. Manual GCR adjustment in addition to custom created ICC profiles decreased MI further, but at the same time increased ∆E*_ab to some extent. Increased GCR settings had considerable impact on MI, which varied per color shade. The ICC profiles for the 7 g/m² release coat plus tie coat and 10.5 g/m² release coat plus tie coat substrate were created with 160 % total ink limit values, whereas 7 g/m² release coat and 10.5 g/m² release coat samples without any tie coat were profiled with 180 % and 200 % total ink limit, respectively. Higher total ink limit samples on 10.5 g/m² release coat with no tie coat showed the highest color gamut volume and lowest total ink limit, while 7 g/m² release coat plus tie coat showed the smallest color gamut volume. ANOVA statistical analysis showed that GCR setting was the most influential factor on MI followed by the use of the tie coat. Release coat weight was an insignificant factor for MI.