Establishing Standards for Color and Print Quality in Large Format Inkjet Printing

Abstract

Large format inkjet printing systems have evolved over the last decade and now offer high levels of speed and print and color quality. There are, however, no established standards or test protocols with which to evaluate this technology, and users must rely on manufacturers’ marketing claims and counter claims. Wide and grand format devices may use solvent inks, UV-curable inks (cured via exposure to ultra-violet light), or latex ink. The media typically used by this category of device range from card stock to cast or calendared vinyl to rigid media. Inks used may be CMYK (cyan, magenta, yellow, black), light inks, metallic, or white. Viewing distances for these products range from point of purchase to greater distances for street signs, banners, and billboards. This research first identifies test areas that are relevant to this type of printing system; next, test procedures are developed; and finally, practical testing using commercially available large format roll to roll and flatbed inkjet printing systems is conducted. The aim of this research is to provide real practical data from the field as input to the ISO committee that is developing ISO 15311 that relates to Large Format Signage Printing.As part of the IDEAlliance Inkjet RoundUP, 24 sets of different print samples were obtained from the following supplier companies: Agfa, Durst, EFI, Epson, Fujifilm, HP, Mimaki, Mutoh, Océ, Roland, and Seiko. Tests were conducted for different test areas including color gamut, color management accuracy, print uniformity, repeatability from day to day, CMYK cross-hair registration, ink consumption, print speed, rub resistance as it relates to floor graphics, and weathering as applicable for outdoor signage. Individual test results are presented, and while we do not seek to create “winners” and “losers”, we seek to identify achievable and appropriate “pass/fail” metrics for international standards and local certification/validation programs. In general, for color management, for example, we see that the systems produced extremely accurate color accuracy and are able to match GRACoL to within 1‐2 CIEDE2000.This research also seeks to identify a color characterization data set that can accurately represent the color characteristics of wide format inkjet printing. There exist well-established data sets for offset and gravure printing (for example SWOP, FOGRA, Japan Color), but there are no accepted data sets for large format inkjet printing. One standard being developed, ISO 15339, proposes Characterization Reference Print Condition 7 (CRPC 7) for “Extra large gamut printing processes”. In this research, we evaluate the applicability of using CRPC 7 to represent the color response of commercial large format inkjet printing systems.