Removal of drawing traces of grayscale laser lithography by reflow process

Abstract

In a conventional method where patterned photoresist structures are in direct contact with the metal-cylindrical roller’s surface employing a relief printing, the adhesion area normally does not have a sufficient strength to hold against a subsequent contact pressure and a moment of force that are encountered during the rotation of the roller. Therefore, to improve the robustness of the protuberant photoresist structures, we introduced a residual layer of photoresist (not exposed to any UV light), where the protuberant photoresist structures with sloped sidewalls were cemented onto the residual layer. And then this whole system was used to cover around the surface of the metal-cylindrical-roller. It has been well observed, and reported that a laser drawing system using grayscale lithography leaves traces on photoresist surfaces. However, these traces can now be removed by performing a reflow process under the optimal conditions. As a result of investigating the shape’s transition of the protuberant photoresist structures at different reflow times, and of the durability experiment of 10 times press operations using a flat press-plate, the practicality of our technique combining the grayscale laser lithography and the reflow process was confirmed.