Advanced screen-offset printing for fabricating thick electrodes on the concave surface of cylindrically curved glass

Screen printing is widely used to form conductive patterns due to its simple process, inexpensive equipment and masks, and fewer printing errors. In the field of electronics, there has recently been a growing demand to print both low-width and high-thickness electrodes, not only on flat surfaces but also on cylindrically curved ones. However, screen printing cannot form fine patterns due to ink bleeding, and in principle, printing on concave surfaces is impossible with conventional screen printing. Further, overprinting forms a thick pattern that requires subjecting the conductive ink to a drying process before printing the next layer of ink, leading to longer processing times. To address these issues, we developed an advanced screen printing technique called screen-offset curved-surface printing to form fine patterns on a curved substrate. In this method, ink is screen-printed onto a roll-type silicone blanket, and the ink is then transferred from the blanket onto a final substrate. During the transfer process, the roll-type blanket is moved in the vertical direction with a rotational motion along the surface of the curved substrate. It is this compound motion of the blanket that enables printing on a curved surface. Moreover, a simple overprinting technique for thick patterns was successfully performed on the curved substrate. This technique leverages the fact that the silicone blanket absorbs the organic solvents in the ink; the increase in the viscosity of the first layer of ink, owing to the solvent absorption, enables the next layer of ink to be easily overprinted on the blanket. In this paper, the developed printing method is presented in detail.