The influence of printing substrate on macro non-uniformity and line reproduction quality of imprints printed with electrophotographic process

Digital printing has matured and it is now present in daily production. This is true for both the large format inkjet printing and digital commercial printing (with toner based and increasingly with ink jet technique). In the graphic arts industry in particular the latter use case shows tremendous growth figures where small and medium run lengths are taken over increasingly from the offset market (Kraushaar, 2010). As digital printing industry grows every day a lot of work has been done in improving and developing new technologies and products. This increased growth demands higher level of quality assessment in order to be able to compare different products and technologies and evaluate them (Pedersen et al., 2011). Most production digital printing processes depend on the use of certified paper to perform to their best capacity. Any adjustments that need to be made to the actual press require the intervention of technical support personnel other than the press operator (Chung & Rees, 2007). Print quality is very important in each printing technology, and also for digital printing (Rilovski et al., 2012). A common way for analyzing the print quality is to quantitatively assess image color and tone value reproduction using corresponding measuring device. This way of analyzing print quality is easy, since tone and color are easily perceptible, but they are not enough for determining print quality (Dhopade, 2009; Kiurski & Oros, 2012). Several experiments proved that print quality is not a monotonic function of hue, saturation and brightness (Fedorovskaya, Ridder & Blommaert, 1997; Pedersen et al., 2009). Quantitative print quality assessment depends on a number of quality attributes (Pedersen et al., 2011; Rilovski et al., 2012). There are several of them such as contrast, sharpness, macro-uniformity, etc., which are not associated with tone and color but have considerable influence on print quality. They are directly connected with line and dot quality, which are structural elements of any image (Dhopade, 2009). So far many researches have been done that confirmed the importance of different quality attributes, but there is no overall agreement which of them are most important (Pedersen et al., 2011; Rilovski et al., 2012). One of the reason is multidimensionality and complexity of image quality (Pedersen et al., 2011).