# Influence of Printing Substrate on Quality of Line and Text Reproduction in Flexography
## 5 Conclusions  
Analysis of measurement results indicates correlation in the deformation of lines and text on printouts. Correlation in deformation of fine elements is visible in line diagrams and is related to the type of printing substrate and the type of reproduction mode in positive or negative shapes.  
Spreading of fine elements on printouts was estimated based on their area measurements. The biggest deviations from target were recorded on OPP film (22.7% in positive shape, \(-\)18.2% in negative shape). Therefore, fine elements printed in the positive shape have the tendency to expand, and those printed in the negative shape have the tendency to close. Deviation of line area in relation to the text area is negligibly small for all three printing substrates (up to 8% in a negative shape and up to 5% in a positive shape). In spreading can have a negative effect on the print quality of fine elements, especially tiny text in a negative shape on a colored background, which can result in poor text legibility. On uncoated paper, the ink expands more into the structure of the material itself; therefore, the surface spread of the ink is less.  
Edge degradation of fine elements on printouts was evaluated based on perimeter measurements and the 2D profile plot. The analysis of both examined parameters also yielded correlating data. Significantly increased edge noise (edge raggedness) was recorded in uncoated paper (up to 40% deviation) due to easier penetration and capillary spreading of ink. The two remaining substrates show similar values (up to 20% deviation) with a slightly smaller deviation from target in coated paper. The lowest edge sharpness was recorded on uncoated paper (distance is 80 \(\upmu\)m), and on OPP film and coated paper is it higher and amounts to 60 \(\upmu\)m. Excessive edge noise of fine elements affects the clarity and visibility of the elements as well as the shape fidelity and legibility of the text. Percentage of area and perimeter deviation of fine element increases with the decrease of the text size and line thickness.  
Visual evaluation of ink layer uniformity of fine elements on the printouts based on the number of dominant peaks showed significantly smaller homogeneity on the uncoated paper. Some unexpected uniformity of the ink layer is higher on coated paper compared with OPP film, although the ink layer on OPP film spreads only on the surface of the substrate.  
It can be concluded that the coated paper showed the best results in all research parameters, which were slightly better results than those on OPP film. The analysis of microscopic images showed that the deformation of fine elements occurs due to a mechanism involving the spreading and penetration of ink. The share of each occurrence in deformation depends on the surface characteristics of the printing substrate. The evaluation of qualitative reproduction parameters has yielded important indicators that  
Figure 10: 3D topographic view of line 170 \(\upmu\)m width at three different printing substrates.  
can significantly improve the production process and result in an increase in the print quality of fine elements.  
Data curation, D.V.; Investigation, I.M.; Methodology, D.C.; Visualization, K.H. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors declare no conflict of interest.