The Journal of Korea Institute of Information, Electronics, and Communication Technology (한국정보전자통신기술학회논문지)

Korea Information Electronic Communication Technology (한국정보전자통신기술학회)
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Liquid crystal alignment on rubbed self-assembled monolayers according to alkyl chain length

알킬 사슬 길이에 따른 러빙 처리된 자기 조립 단분자막의 액정 배향 연구

  • Park, Hong-Gyu (Department of Electrical, Electronic and Control, Changwon National University) ;
  • Park, Mu-Hun (Department of Electrical, Electronic and Control, Changwon National University)
  • Received : 2021.09.24
  • Accepted : 2021.10.06
  • Published : 2021.10.30
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Abstract

A homeotropic liquid crystal (LC) alignment state on rubbed fluorinated self-assembled monolayers (FSAMs) is described according to alkyl chain length. A simple procedure, gas-phase method, for the preparation of FSAM was used. The average optical transmittance in the visible light range of FSAMs were 76.63% to 78.21%, which were superior to the conventional polyimide layer having a transmittance of 75.89%. In addition, the excellent homeotropic LC alignment characteristics of FSAMs were observed through pretilt angle measurement and polarized optical microscope images. By measuring the contact angles and the surface energies of FSAMs, it was confirmed that pretilt angles of LC molecules increased according to the alkyl chain length. High optical transparency and uniform homeotropic LC alignment characteristics of FSAMs showed the possibility of FSAMs as an LC alignment layers.

본 논문에서는 알킬 사슬 길이에 따른 러빙 처리된 불소화 자기 조립 단분자막(fluorinated self-assembled monolayers; FSAM)의 수직 액정 배향 상태를 보고한다. FSAM의 증착을 위해 간단한 공정인 기체-상 방법이 사용되었다. FSAM의 가시광선 영역대 광학 평균 투과율은 77.63%~78.21%로 75.89%의 투과율을 갖는 기존의 폴리이미드막보다 우수하였다. 또한 프리틸트각 측정과 편광현미경 사진을 통해 FSAM의 우수한 수직 배향 특성을 관찰하였다. 접촉각과 FSAM의 표면에너지 측정을 통해 알킬 사슬 길이에 따른 프리틸트각이 증가하는 것을 확인하였다. FSAM의 높은 광학 투과율과 균일한 수직 배향 특성은 FSAM이 액정 배향막으로서의 가능성을 보여주었다.

Keywords

Acknowledgement

This research was supported by Changwon National University in 2021~2022.

References

  1. S. Ishihara, H. Wakemoto, K. Nakazima, Y. Matsuo, "The effect of rubbed polymer films on the liquid crystal alignment", Liq. Cryst., Vol. 4 (6) pp. 669-675, June, 1989. https://doi.org/10.1080/02678298908033202
  2. J. J. Schwartz, A. M. Mendoza, N. Wattanatorn, Y. Zhao, V. T. Nguyen, A. M. Spokoyny, C. A. Mirkin, T. Base, and Paul S. Weiss, "Surface dipole control of liquid crystal alignment", J. Am. Chem. Soc., Vol. 138 (18), pp. 5957-5967, April, 2016. https://doi.org/10.1021/jacs.6b02026
  3. X. Wei, S.-C. Hong, X. Zhuang, T. Goto, and Y. R. Shen, "Nonlinear optical studies of liquid crystal alignment on a rubbed polyvinyl alcohol surface", Phys. Rev. E, Vol. 62 (4), pp. 5160-5172, October, 2000. https://doi.org/10.1103/PhysRevE.62.5160
  4. P. Chaudhari, J. Lacey, J. Doyle, E. Galligan, S.-C. A. Lien, A. Callegari, G. Hougham, N. D. Lang, P. S. Andry, R. John, K.-H. Yang, M. Lu, C. Cai, J. Speidell, S. Purushothaman, J. Ritsko, M. Samant, J. Stohr, Y. Nakagawa, Y. Katoh, Y. Saitoh, K. Sakai, H. Satoh, S. Odahara, H. Nakano, J. Nakagaki, Y. Shiota, "Atomic-beam alignment of inorganic materials for liquid-crystal displays", Nature, Vol. 411, pp. 56-59, May, 2001. https://doi.org/10.1038/35075021
  5. H.-G. Park, Y.-H. Kim, B.-Y. Oh, W.-K. Lee, B.-Y. Kim, and D.-S. Seo, "Vertically aligned liquid crystals on a γ-Al2O3 alignment film using ion-beam irradiation", Appl. Phys. Lett. Vol. 93 (23), 233507, December, 2008. https://doi.org/10.1063/1.3046728
  6. G. Zhu, F. Wang, W. Liu, X. Gong, P. Geng, Z. Gao, Y. Wang, "Synthesis of photosensitive polyimide for liquid crystal alignment under non-polarised UV ageing lamp irradiation and a study on the possible mechanism of alignment", Liq. Cryst., Vol. 47 (4), pp. 489-499, 2000. https://doi.org/10.1080/02678292.2019.1658816
  7. B.-Y. Liu, C.-H. Meng, L.-J. Chen, "Role of monomer alkyl chain length in pretilt angle control of polymer-stabilized liquid crystal alignment system", J. Phys. Chem. C, Vol. 121 (38), pp. 21037-21044, September, 2017. https://doi.org/10.1021/acs.jpcc.7b07160
  8. J. H. Lee, J. Won, H.-C. Jeong, D. H. Kim, D. W. Lee, J.-M. Han, B.-Y. Oh, D.-S. Seo, "Physicochemical analysis of ion beam-induced surface modifications on polyethylene glycol films for liquid crystal alignment", Liq. Cryst., Vol. 46 (12), pp. 1799-1807, 2019. https://doi.org/10.1080/02678292.2019.1606351
  9. D. M. Walba, C. A. Liberko, E. Korblova, M. Farrow, T. E. Furtak, B. C. Chow, D. K. Schwartz, A. D. Freeman, K. Douglas, S. D. Williams, A. F. kittnick, N. A. Clak, "Self-assembled monolayers for liquid crystal alignment: simple preparation on glass using alkyltrialkoxysilanes", Liq. Cryst., Vol. 31 (4), pp. 481-489, 2010. https://doi.org/10.1080/02678290410001666075
  10. S.-G, Park, and H.-G. Park, "Alignment of liquid crystal molecules on self-assembled monolayer with fluorinated alkyl chain at different deposition time", Opt. Mater., Vol. 85, pp. 298-302, November, 2018. https://doi.org/10.1016/j.optmat.2018.08.068
  11. F. Huang, X. Li, S. Wang, "Highly efficient hole injection/transport layer-free OLEDs based on self-assembled monolayer modified ITO by solution-process", Nano Energy, Vol. 78, 105399, December, 2020. https://doi.org/10.1016/j.nanoen.2020.105399
  12. D. An, H. Liu, S. Wang, X. Li, "Modification of ITO anodes with self-assembled monolayers for enhancing hole injection in OLEDs", Appl. Phys. Lett., Vol. 114 (15), 153301, April, 2019. https://doi.org/10.1063/1.5086800
  13. D. A. Kara, K. Kara, G. Oylumluoglu, M. Z. Yigit, M. Can, J. J. Kim, E. K. Burnett, D. L. G. Arellano, S. Buyukcelebi, F. Ozel, O. Usluer, A. L. Briseno, M. Kus, "Enhanced device efficiency and long-term stability viaboronic acid-based self-assembled monolayer modification of indium tin oxide in a planar perovskite solar cell", ACS Appl. Mater. Interfaces, Vol. 10 (35), pp. 30000-30007, September, 2018. https://doi.org/10.1021/acsami.8b10445
  14. D.-S. Seo, S. Kobayashi, M. Nishikawa, J.-H. Kim, Y. Yabe, "Odd-even effects of the polar anchoring strength in nematic liquid crystal on rubbed polyimide Langmuir-Blodgett films with alkyl chain lengths", Appl. Phys. Lett., Vol. 66 (11), pp. 1334-1336, March, 1995. https://doi.org/10.1063/1.113233
  15. C. Lee, T. H. Woo, M. Lee, "Effect of alkyl side chain of soluble polyimide orienting layer on liquid crystal alignment", Mol. Cryst. Liq. Cryst., Vol. 316 (1), pp. 205-208, October, 1998. https://doi.org/10.1080/10587259808044492
  16. B.-Y. Liu, C.-H. Meng, L.-J. Chen, "Role of monomer alkyl chain length in pretilt angle control of polymer-stabilized liquid crystal a lignment system", J. Phys. Chem. C, Vol. 121 (38), pp. 21037-21044, September, 2017. https://doi.org/10.1021/acs.jpcc.7b07160
  17. S.-G. Park, T. Mori, "Electro-optics characteristics of organic thin-film by employing fluorinated self-assembled monolayer", ECS Solid State Lett., Vol. 3 (7), pp. R29-R31, January, 2014. https://doi.org/10.1149/2.0031407ssl
  18. J. Norris, R. F. Giese, C. J. van Oss and P. M. Costanzo, "Hydrophobic nature of organo-clays as a Lewis acid/base phenomenon", Clays Clay Miner., Vol. 40 (3), pp. 327-334, June, 1992. https://doi.org/10.1346/CCMN.1992.0400313
  19. J. van Oss, M. K. Chaudhury and R. J. Good, "Interfacial Lifshitz-van der Waals and polar interactions in macroscopic systems", Chem. Rev., Vol. 88 (6), pp. 927-941, September, 1988. https://doi.org/10.1021/cr00088a006
  20. T. Greagh and A. R. Kmetz, "Mechanism of surface alignment in nematic liquid crystals", Mol. Cryst. Liq. Cryst., Vol. 24 (1-2), pp. 59-68, 1973. https://doi.org/10.1080/15421407308083389
  21. K. Y. Han, T. Miyashita, T. Uchida, "Accurate measurement of the pretilt angle in a liquid crystal cell by an improved crystal rotation method", Mol. Cryst. Liq. Cryst., Vol. 241 (1), pp. 147-157, 1994. https://doi.org/10.1080/10587259408029751