Durable Soft Mold for Imprinting of High-Adhesive Resin

A variety of polymer resins have been used to fabricate micro/nano structures via imprint lithography. In addition, with an interest in productivity, there is an increasing demand for the study of the process of easily demolding a cured resin from a mold for continuous fabrication of micro/nanostructures applying imprint lithography to the roll-type equipment. Among these polymer resins, Norland optical adhesive (NOA) in particular is widely used to fabricate micro/nano structure-based functional surfaces because of its shape memory characteristics, biocompatibility, and great optical characteristics. However, the cured NOA is originally used as an epoxy-based adhesive with its high adhesion. NOA has many advantages as a UV-curable adhesive, but as a resin in the imprint process, such adhesion brings a limitation. This high adhesion of cured NOA causes defects in the mold during the demolding process, so it is difficult to apply it to the continuous fabrication process. Here, we present a durable polyurethane acrylate (PUA) soft mold capable of clean demolding of an epoxy-based polymer resin having high adhesion by depositing metal on a surface. Au and Ni were deposited to a thickness of 100 Å by using an E-beam evaporator. To verify the surface characteristics, each metal-deposited soft mold was compared with the previously used soft mold by measuring the contact angle and calculating surface energy. To test a performance of our soft mold, we imprinted nanoline pattern with NOA as a resin using metal-deposited soft mold in roll to roll (R2R) process for more than 240 replications for 90 min of operation time. It is expected that this study can be used for mass production of pattern with epoxy-based patterns required in many fields.