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Highly flexible cover window using ultra-thin glass for foldable displays

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Abstract

The market for next-generation flexible displays is rapidly expanding with the launch of foldable electronic products. Consequently, the flexible electronic material and device industries are continuously growing. Specifically, the cover window used in foldable displays is a very important component that must have excellent optical, physical, and mechanical characteristics while withstanding high external stresses caused by the bending radius, unlike the existing rigid-type cover windows. Considerable research efforts have been dedicated toward improving their performance. In this study, a cover window substrate for a foldable display having high flexibility was developed. To this end, ultra-thin glass (UTG) with excellent flexibility and transparency was used to overcome the low surface hardness of the typical polymer substrate used in existing foldable substrates. In addition, for efficient stress control, the design of the multilayer structure was optimized by generating multiple neutral planes through the use of an optical clear adhesive (OCA) buffer layer. The structure of the cover window was designed using the finite element simulation technique, and actual samples of the cover window with the optimized structure were produced to evaluate their physical, mechanical, and optical characteristics. As a result, the optimized foldable cover window showed a surface hardness of 9 H and a light transmittance of 90 %; especially, it exhibited an excellent bending reliability with 200000 bending repetitions without failure at the small bending radius of 1.5 R.

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Abbreviations

Es :

Young’s modulus of the substrate

h s :

Thickness of the substrate

h f :

Thickness of the film

V s :

Poisson’s ratio of the substrate

R:

Bending radius

σ f :

Average stress received by film

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Acknowledgments

This work was supported by the Industry Technology R&D Program (20010371) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea).

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Authors and Affiliations

  1. Department of Display Engineering, Dankook University, 119, Dandae-ro, Chungnam, Cheonan-si, 31116, Korea

    Myeong-Hun Ha, Jong-Keun Choi, Byung-Min Park & Kwan-Young Han

Authors
  1. Myeong-Hun Ha
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  2. Jong-Keun Choi
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  3. Byung-Min Park
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  4. Kwan-Young Han
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Corresponding author

Correspondence to Kwan-Young Han.

Additional information

Myeong-Hun Ha is a Master course of Department of Electronics and Electrical Engineering, Dankook University in Korea. He received his Bachelor’s degree in Display Engineering from Dankook University in Korea. His research interests include flexible substrate, structure simulation, instrument design and PLC control.

Jong-Keun Choi is a Doctor course of Department of Electronics and Electrical Engineering, Dankook University in Korea. He received his Master in Electronics and Electrical Engineering from Dankook University in Korea. His research interests include anisotropic conductive film and flexible substrate.

Byung-Min Park is a Research Professor of the Department of Display Engineering, Dankook University, Cheonansi, in Korea. He received his Ph.D. in Electronics and Electrical Engineering from Dankook University in Korea. His research interests include OLED & QD device, encapsulation technicque.

Kwan-Young Han is a Professor of the Department of Display Engineering, Dankook University, Cheonan-si, in Korea. He received his Ph.D. in Electronics and flat panel display molecular orientation and control at Tohoku University in Japan. His research items are module development for flat panel display including a OLED TFE processor and equipment of OLED module.

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Ha, MH., Choi, JK., Park, BM. et al. Highly flexible cover window using ultra-thin glass for foldable displays. J Mech Sci Technol 35, 661–668 (2021). https://doi.org/10.1007/s12206-021-0126-y

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  • DOI: https://doi.org/10.1007/s12206-021-0126-y

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