Journal of the Korean institute of surface engineering (한국표면공학회지)

The Korean Institute of Surface Engineering (한국표면공학회)
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Processing of ta-C Protective Films on Mold for Glass Lens

유리렌즈 성형용 금형의 ta-C 보호 필름 제조에 관한 연구

  • Oh, Seung-Keun (Department of Materials Science and Engineering, Chonnam National University) ;
  • Kim, Young-Man (Department of Materials Science and Engineering, Chonnam National University)
  • 오승근 (전남대학교 신소재공학부) ;
  • 김영만 (전남대학교 신소재공학부)
  • Received : 2011.07.19
  • Accepted : 2011.10.28
  • Published : 2011.10.31
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Abstract

Recently aspheric lenses are widely used for superpricision optical instruments, such as cellular phone camera modules, digital cameras and optical communication modules. The aspherical lenses are processed using mold core under high temperature compressive forming pressure. It is imperative to develop superhard protective films for the life extension of lens forming mold core. Especially ta-C films with higher $sp^3$ fractions receive attentions for the life extension of lens forming mold and, in turn, the cost reduction of lenses due to their suprior high temperature stability, high hardness and smooth surfaces. In this study ta-C films were processed on WC mold as a function of substrate bias voltage using FVA (Filtered Vacuum Arc) method. The processed films were characterized by Raman spectroscopy and nano-indentation to investigate bonding nature and hardness, respectively. The film with maximun 87% of $sp^3$ fraction was obtained at the substrate bias voltage of -60 V, which was closest to ta-C film. ta-C films showed better high temperature stability by sustaining relatively high fraction of $sp^3$ bonding even after 2,000 glass lens forming applications.

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