Fabrication of seamless roller mold with 3D micropatterns using inner curved surface photolithography

• We present an innovative technique for fabricating imprinting roller molds with seamless patterns.
• A hollow roller is coated with a thin PR layer and then exposed using a proximity mode lithography exposure technique.
• Microstructure patterns are transferred to a roller by means of a polydimethyl-siloxane (PDMS) casting technique.
• Imprinted diffusion film has a haze of 97.1% and a total transmittance of 91.6%.

Continuous roller imprinting is one of the most promising means of fabricating micro/nano structures over a large area. However, the fabrication of roller molds with seamless and three-dimensional (3D) complex patterns poses a significant challenge. Accordingly, this paper presents an innovative approach for fabricating a seamless hollow roller master mold patterned with discrete or continuous 3D structures. The major steps in the proposed fabrication method include an inner pneumatic rotary photoresist (PR) coating process followed by a step-and-rotate lithography process or a continuous rotation lithography process. Having fabricated the master mold, the microstructure patterns are transferred to a roller by means of a polydimethyl-siloxane (PDMS) casting technique. The effectiveness of the proposed method is demonstrated by patterning a PDMS-casted roller mold with wavy microstructures and then using the roller mold to fabricate a diffusion optical film. The experimental results show that the diffusion film has a haze of 97.1% and a total transmittance of 91.6%.

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