Journal of the Semiconductor & Display Technology (반도체디스플레이기술학회지)

The Korean Society Of Semiconductor & Display Technology (한국반도체디스플레이기술학회)
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Evaluation of Residual Strains under Pure Bending Loading for Colorless and Optically Transparent Polyimide Film for Flexible Display

유연 디스플레이용 무색 투명 폴리이미드 필름의 굽힘 잔류 변형률 평가

  • Choi, Min-Sung (Department of Mechanical System Engineering, Kumoh National Institute of Technology) ;
  • Park, Min-Seok (Department of Mechanical System Engineering, Kumoh National Institute of Technology) ;
  • Park, Han-Yeong (Department of Mechanical System Engineering, Kumoh National Institute of Technology) ;
  • Oh, Chung-Seog (Department of Mechanical System Engineering, Kumoh National Institute of Technology)
  • 최민성 (금오공과대학교 기계시스템공학과) ;
  • 박민석 (금오공과대학교 기계시스템공학과) ;
  • 박한영 (금오공과대학교 기계시스템공학과) ;
  • 오충석 (금오공과대학교 기계시스템공학과)
  • Received : 2021.10.23
  • Accepted : 2021.12.14
  • Published : 2021.12.31
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Abstract

The display industry is transitioning from traditional rigid products such as flat panel displays to flexible or wearable ones designed to be folded or rolled. Accordingly, colorless and optically transparent polyimide (CPI) films are one of the prime candidates to substitute traditional cover glass as a passivation layer to accommodate product flexibility. However, CPI films subjected to repetitive pure bending loads inevitably entail an accumulation of residual strain that can eventually cause wrinkles or delamination in the underlying component after a certain number of static and cyclic loading. The purpose of this study is to establish an experimental method to systematically evaluate the bending residual strain of CPI films. Films were monotonically and cyclically wrapped on mandrels of various diameters to ensure a constant strain in each. After unwrapping the wound CPI film, the residual radius of curvature remaining on the film was measured and converted into residual strain. The critical radius of curvature at which residual strain does not remain was about 5 mm, and the residual strain decreased in proportion to the log time. It is expected that flexible displays can be reliably designed using the data between the applied bending strain and the residual strain.

Keywords

Acknowledgement

이 연구는 2019년 국립대학 육성사업비로 지원되었음.

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