Optimisation of screen printing process for functional printing

Purpose The purpose of this study is to explain the effects of screen printing parameters on the quantity of ink deposited and the print quality in the context of printing of functional inks. Both these aspects of printing are crucial in the case of conventional and functional printing. This is because, in the case of conventional printing, the quantity of ink deposit affects the color strength while in the case of functional printing, it directly affects the resulting functionality of the ink layer. Design/methodology/approach In this work, an automatic lab-scale screen printer was used to print functional inks on a paper board substrate. The printing parameters, i.e. printing pressure and squeegee angle were altered and the resulting effects on the quantity of ink that was deposited were recorded. The quantity of ink deposit was related to its surface resistivity. In addition, the quality of the print was also assessed by examining the design registration quality. Findings The authors found that altering the squeegee angle has a significant effect on the properties of the resulting ink deposit. More importantly, the authors found that the deflection in the rubber blade squeegee was greatly dependent on the initial angle of the squeegee at the start of the printing stroke. For each set value of the squeegee angle that was considered, the actual angle during printing was recorded and used in the analysis. A printing pressure of three bars and squeegee angle of 20° resulted in the maximum weight of ink deposit with a correspondingly lowest surface resistivity. Practical implications This study is envisaged to have considerable practical implications in the rapidly growing field of functional printing of flexible substrates including, but not limited to, textiles. This is because, the study provides an insight into the effects of printing parameters on the characteristics of a functional ink deposit. Originality/value Screen printing of flexible substrates is a well-developed and arguably the most widely used printing technique, particularly for textiles. Numerous studies report on the analysis of various aspects of screen printing. However, to the best of the knowledge, the effects of printing parameters on the characteristics of functional inks, such as electrically conductive inks, have not been studied in this manner.

One-step green approach for functional printing and finishing of textiles using silver and gold NPs

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Functional inks and printing of two-dimensional materials

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Functional Printing of Silver Nano Ink on Injection Molded Polymeric Substrates

Over the last decades ink-jet printing has developed in many applications. The direct writing of materials such as silver (for conductive circuits) or polymers (for insulation or second layer) is an attractive method to reduce costs and save raw materials. In this article we investigate the geometrical and electrical properties of conductive circuit lines on thermoplastic substrates, depending on the printing parameters such as line width, orientation of the lines and density of the printed drops (dots per inch = dpi)First the surface of the substrates is scanned by a confocal laser scanner. The substrates (size 60mm x60 mm) are subdivided in 80 x 80 parts with a side length of 0.8mm. The 2D roughness (Sa) of these little parts is calculated and as a result the locally solved roughness of the substrates is determined. Homogeneity and surface quality of the surfaces can be evaluated.On the different polymeric substrates conductors (length 25mm) are printed with a printing head with 16 nozzles and with different orientations (parallel, horizontal and in an angle of 45° to the movement of the printing head). Also different dpi numbers (600, 900 and 1200) are used and the line width in the bit pattern is increased from 1 pixel to 5 pixels. The line width in μm depending on the line width in pixel is measured. The quality of the printed lines is quantified by calculating the deviation of the printed lines to a “perfect straight line” with the same width. The resistivity of the conducting lines and the reliability of the process are determined.