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Sensors 2017, 17(12), 2825; https://doi.org/10.3390/s17122825

Invisible Security Printing on Photoresist Polymer Readable by Terahertz Spectroscopy

1
Research Group of Food Safety, Korea Food Research Institute, 245, Nongsaengmyeong-ro, Iseo-myeon, Wanju-gun, Jeollabuk-do 55365, Korea
2
Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea
*
Author to whom correspondence should be addressed.
Received: 24 October 2017 / Revised: 28 November 2017 / Accepted: 4 December 2017 / Published: 6 December 2017
(This article belongs to the Section Physical Sensors)
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Abstract

We experimentally modulate the refractive index and the absorption coefficient of an SU-8 dry film in the terahertz region by UV light (362 nm) exposure with time dependency. Consequently, the refractive index of SU-8 film is increased by approximately 6% after UV light exposure. Moreover, the absorption coefficient also changes significantly. Using the reflective terahertz imaging technique, in addition, we can read security information printed by UV treatment on an SU-8 film that is transparent in the visible spectrum. From these results, we successfully demonstrate security printing and reading by using photoresist materials and the terahertz technique. This investigation would provide a new insight into anti-counterfeiting applications in fields that need security. View Full-Text
Keywords: terahertz spectroscopy; anti-counterfeiting; security; photoresist material terahertz spectroscopy; anti-counterfeiting; security; photoresist material
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Shin, H.J.; Lim, M.-C.; Park, K.; Kim, S.-H.; Choi, S.-W.; Ok, G. Invisible Security Printing on Photoresist Polymer Readable by Terahertz Spectroscopy. Sensors 2017, 17, 2825.

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