Removal of drawing traces of grayscale laser lithography by reflow process

• Mechanical strength of convex structures for resin relief printing was improved.
• Sloped sidewalls were added to the resin structures, and were combined with a residual layer.
• Drawing traces often encountered when working with grayscale laser lithography were removed by the process of reflowing.
• A flat press-plate was fabricated as a trial run using a SUS420J substrate.
• This flat press-plate passed a durability test by 10 consecutive press operations.

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.

Figure optionsDownload as PowerPoint slide