Thermal roll-to-roll imprinted nanogratings on plastic film

Nanogratings can be used in various fields, such as optics, electronics, or energy conversion. In the next generation, the desired area of nanogratings will be in excess of 1 m2 and there is therefore a demand for an effective nanopatterning technique capable of fabricating future devices on this scale at low cost and in high volume. The roll-to-roll nanoimprint (R2RNIL) technique has received much attention because of its simplicity and high throughput. Thermal R2RNIL (T-R2RNIL), in particular, is expected to provide a major breakthrough because, for example, the costs of materials for the technique are much lower than those for ultraviolet R2RNIL, which requires a photocurable resin. Furthermore, T-R2RNIL is a dry process and is therefore more suited to industrial application. In T-R2RNIL with a nanograting mold, understanding the replication behavior, which varies with the process temperature, is a key to obtaining the required features. The authors examined T-R2RNIL high-speed patterning of nanogratings on a cellulose acetate film at various process temperatures and feature sizes of the mold. The replication behavior of a nanograting mold was found to differ from that of a micrograting mold. In addition, the depth of the imprinted pattern could be controlled by varying the process temperature and the pressure. This controllability permits the ready fabrication of nanogratings of various heights from a single mold.