An ink transfer process from the printing roll to the moving web was investigated using a computational fluid dynamics technique for the roll-to-roll application in the area of printed electronics. Emphasis was made on the shape of the transferred ink pattern in a realistic configuration. The shear-thinning effect of the conductive ink was treated using a generalized non-Newtonian fluid model. That is, the coefficients of the Carreau model were determined using the fluid dynamic property information of the commercially available conductive ink used in the roll-to-roll process. Also, the web handling speed was matched with that of the typical roll-to-roll process applied in printed electronics. Computational results show that the spatial variation of the shear rate is quite significant in the present configuration; therefore, the Carreau model better predicts the shape of the measurement data than Newtonian fluid in the range of the line thickness of 100–500 µm. It is also noted that the non-uniformity of the transferred ink that is experimentally observed is better predicted by the non-Newtonian model. It is conjectured that the distortion of the shape and the non-uniform distribution of the transferred ink are the prime sources for deterioration in printing quality. However, the fact that web handling speeds of up to 30 mpm (=0.5 m/s) do not significantly aggravate the degree of distortion still supports the main advantage of a cost-effective, continuously running roll-to-roll process in this speed range.
