PRELIMINARY STUDY OF PRINT MOTTLE ANALYSIS IN FLEXOGRAPHY USING GLCM METHOD
Flexography is a printing technique frequently used for printing the large solid tone areas on different substrates. The print quality of such an imprint is, among others, dependable on screen ruling of used anilox roll. If it is not chosen properly, it might influence often seen print defect in flexography – print mottle. Print mottle is manifested as an uneven ink lay or undesired unevenness in perceived print density especially visible in large solid tone areas. In this preliminary study, we have used Gray Level Co-concurrence Matrix (GLCM) for the print mottle evaluation on one colour (cyan) flexo printed polymer samples printed in full coverage using anilox rollers of different screen ruling. GLCM was chosen with the idea that a simple, statistical approach used for texture analysis can also be successfully utilized in the mottle analysis. The following parameters were used for print mottle characterization: contrast, homogeneity, correlation, energy and entropy. The analysis was done on samples scanned using different scanning resolutions. The study has implied that GLCM method has a potential to be used for flexo print mottle evaluation where scanning resolution has more influence on contrast, entropy and correlation rather than on homogeneity and energy. Results have also indicated that with the higher ink coverage, the higher print mottle can be expected.