Positional accuracy of micropatterns in the roll-to-roll imprinting process using a wrapped roll mold

Abstract

Various micropatterns in flexible devices can be fabricated using the roll-to-roll (R2R) imprinting process, wherein a raw flexible plastic film is released from a roller and subjected to several patterning processes such as imprint lithography. In case a thin-film-transistor liquid-crystal display (TFT-LCD) is formed on the flexible film, overlay accuracy becomes the most important factor in the patterning process. To achieve positional accuracy, the process parameters that affect dimensional changes should be analyzed. In our system, the roll mold was fabricated by wrapping a thin film sheet to the roller. During the process, the substrate was deformed by web tension and bent by overall system architecture. Thus, web tension, misalignment angle, mold thickness, and substrate bending effects were regarded as the main parameters, which were analyzed and modeled into mathematical formulas. Positional errors and their tolerances were estimated using the formulas, and process parameters were designed to compensate for each error. Finally, the color filters in the flexible TFT-LCD display were manufactured using R2R imprinting and ink-jet printing. Dimensional error can be minimized to approximately ±15 μm for the entire area of 200 mm × 150 mm.