Numerical Study on the Optimization of Roll-to-Roll Ultraviolet Imprint Lithography

Abstract

Roll-to-roll ultraviolet (R2R-UV) imprinting is a low-cost and high-throughput method that includes the manufacturing of large-area functional films. However, the quality of the final product is obstructed by the bubble entrapment during the imprinting process. In this study, a multi-phase volume of fluid (VOF) numerical model was used to remove bubble entrapment during the R2R imprinting process, which covered all parameters. This new modified numerical model with open-channel boundary conditions was based on the single zone that contains the direct contact of UV resin with the imprinting mold during the filling process. In addition, this model simulated the UV resin filling into microcavities at the preceding and succeeding ends of the imprinting mold. Different patterns of imprinting mold were considered to enhance the fidelity of R2R-UV imprinting for the comprehensive analysis. The experimental results validated through numerical simulations revealed that the bubble entrapment can be controlled by varying various parameters such as speed of the imprinting system, viscosity, contact angles, and pattern shape. The proposed model may be useful for a continuous bubble-free R2R imprinting process in industrial applications that includes flexible displays and micro/nano-optics.

Process Optimization for Manufacturing Functional Nanosurfaces by Roll-to-Roll Nanoimprint Lithography

“…To simulate UV resin flow into nanopillars and nanopores under environmental conditions, we used a 2D multiphase volume of fluid model (VOF) model [ 14 , 15 ] with moving walls and OC boundary conditions. The mathematical formulation of multiphase VOF model is explained in [ 5 ]. The fixed Eulerian mesh method was used to define the two phases in multiphase VOF model.…”

“…The smooth fabrication process has various defects because of the incomplete filling of the UV resin into the nanopatterns from the left/right (based on the filling direction) end of the imprint mold. Several studies [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ] were conducted in the literature to optimize the filling processes. Pietarinen et al [ 10 ] introduced the micro-optics replication process with the solvent-assisted filling into the micro-pyramid structures to avoid the defects due to air entrapment.…”

“…The mathematical models are the most thorough techniques to investigate the RTR-UV-NIL process. Numerous studies [ 2 , 3 , 5 , 6 , 7 , 8 , 9 , 12 ] analyzed the RTR system by using numerical modeling for the UV resin filling process and proposed various strategies to attain high fidelity for the continuous fabrication process. Song et al [ 13 ] investigated the influence of backing film together with UV resin flow into the cavities by utilizing coupled Eulerian–Lagrangian technique.…”

“…A two-body system with an interface between the imprint mold and the outside region was used in their numerical model. In our previous work [ 5 ], we utilized multiphase numerical modeling with open-channel (OC) boundary conditions to analyze the filling behavior into the microcavities. The numerical model is based upon a single zone and optimize the filling behavior on the prior and succeeding ends of the imprint mold.…”

Injection-rolling nozzle in an imprint system with continuous injection direct rolling for ultra-thin microstructure guide light plate

“…In addition, various methods have also been applied to the formation of thin film with microstructures, such as hot imprint with roll-to-plate or roll-to-roll, and ultraviolet imprint lithography. [6][7][8][9] Generally, polymer flat plates are required to be pre-created in advance and reheated before processing in hot imprint technologies, which leads to long production cycle and low production efficiency. Moreover, the microstructure uniformity is difficult to be controlled in hot imprinting processes.…”