Roller imprinter

Figure 2.6 (a) Schematic of the metal wire-grid polarizer by depositing metal on topofthe roller imprinted polymer grating (b) SEM picture of a 200 nm period grating with 50 nm Al on top (c) spectral transmittance (TM, TE mode) and... 

Figure 36-2. Processing by roller coating or coating, (a) coating by roller, (b) roller coating with imprinting roller, (c) coating by doctor roller, (d) coating by spray coating (can also be called injection casting).

Several ETFE soft stamps are then transferred on to a tensioned belt, which loops continuously over two rollers. The soft stamp imprints the nanoscale pattern onto the conveying coated substrate (Fig. 13.9). Continuous roU-to-roU imprinting has been demonstrated using a 10 cm wide pattern. The polymer-coated substrate is imprinted and simultaneously UV cured, before the rolling stamp detaches from the imprinted polymer. The UV-curable polymer resist used is low viscosity liquid epoxysilicone [62]. 

Roll-to-roll nanoimprint lithography provides a unique solution to these challenges encountered in the conventional wafer-level NIL process. Imprinting in the roll-to-roll process takes place in a narrow region transverse to the moving direction of the substrate and thus requires much smaller force for pattern replication. Also since the mold is in the form of a roller, the mold-sample separation proceeds in a peeling fashion, which requires much less force, and reduces the probability of defect generation. 

True roll-to-roll nanoimprinting has been a challenge to the community because it requires a complete set of solutions to a number of interrelated material issues. Firstly, a special roller mold is required for continuous roH-to-roll imprinting of nanostructures. One approach is to use a NIL mold that is sufficiently flexible and can be wrapped on the roller surface. In addition, the mold should have sufficient modulus and strength to be able to imprint other materials. Secondly, liquid resists should have good coating properties and low viscosity to ensure fast imprinting and... 

In our experiment, several pieces of ETFE molds of proper size were replicated, wrapped and fixed onto a tensioned belt. For the roD-to-roD NIL process, the resist material is imprinted by the E FTE molds with pressure appHed from the dual rollers and the tensioned belt, which is then cured by a high-power UV source under the web tension provided by the second roller. On the other hand, in the roD-to-plate NIL process, UV curing of the imprinted resist material takes place between the two rollers under the pressure provided by the belt tension. Even though the tangential component of the belt tension between rollers exerted on resist is smaller than that of the roller pressure, it is sufficient to maintain the resist film thickness after passing... 

The roll-to-roll NIL process requires thermal or UV curing steps, which may not be compatible with many functional polymers for example, bio- or sensitive organic semiconductor materials could be damaged by such process conditions. Moreover, creating large-area continuous pattern requires the same size original mold also the imprinted patterns are not tmly continuous due to the presence of a seam region where the two ends of the flexible mold meet on the roller. 

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