Fabrication of Seamless Roller Mold for Continuous Roller Imprinting of Microlens Array Films

Author

Lee, Yung-Chun ; Chen, Hong-Wei ; Hsiao, Fei-Bin

Author_Institution

Dept. of Mech. Eng., Nat. Cheng Kung Univ. (NCKU), Tainan, Taiwan

Volume

21

Issue

2

fYear

2012

fDate

4/1/2012 12:00:00 AM

Firstpage

316

Lastpage

323

Abstract

This paper describes an innovative approach for fabricating a seamless roller mold based on cylindrical photolithography, isotropic chemical etching, and electropolishing. Hexagonally arrayed concave microstructures with a near-semispherical profile are directly and seamlessly fabricated on a metal roller. The fabricated roller mold is then used for continuous roller imprinting of microlens array (MLA) on a thin polyethylene terephthalate (PET) substrate. The fabricated ball-shape microlenses have a footprint diameter of 54 and a sag height of 20.5 and are hexagonally close packed with a filling ratio larger than 91%. This MLA/PET optical film can serve as a brightness enhancement film in flat panel backlighting, and its optical performance is experimentally verified. A 30% increase in the forward on-axis luminance is observed.

Keywords

electrolytic polishing; etching; microlenses; moulding; moulding equipment; optical arrays; optical fabrication; optical films; optical polymers; photolithography; polymer films; rollers (machinery); MLA-PET optical film; PET substrate; ball-shape microlense fabrication; brightness enhancement film; continuous roller imprinting; cylindrical photolithography; electropolishing; filling ratio; flat panel backlighting; footprint diameter; forward on-axis luminance; hexagonally arrayed concave microstructure; hexagonally close packing; isotropic chemical etching; metal roller; microlens array film; near-semispherical profile; optical performance; sag height; seamless roller mold fabrication; thin polyethylene terephthalate; Etching; Lenses; Microcavities; Microstructure; Rough surfaces; Surface roughness; Cylindrical photolithography; microlens array (MLA); optical film; roller imprinting; seamless roller mold;

fLanguage

English

Journal_Title

Microelectromechanical Systems, Journal of

Publisher

ieee

ISSN

1057-7157

Type

jour

DOI

10.1109/JMEMS.2011.2178115

Filename

6119182