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http://dx.doi.org/10.3807/COPP.2018.2.2.185

Ellipsometric Characterization of Rubbed Polyimide Alignment Layer in Relation with Distribution of Liquid Crystal Molecules in Twisted Nematic Cell  

Cho, Sung Yong (Department of Physics, Ajou University)
Park, Sang Uk (Ellipso Technology Co., Ltd.)
Yang, Sung Mo (Department of Physics, Ajou University)
Kim, Sang Youl (Department of Physics, Ajou University)
Publication Information
Current Optics and Photonics / v.2, no.2, 2018 , pp. 185-194 More about this Journal
Abstract
Ultra-small optical anisotropy of a rubbed polyimide (PI) alignment layer is quantitatively characterized using the improved reflection ellipsometer. Twisted nematic (TN) cells are fabricated using the rubbed PIs of known surface anisotropy as alignment layers. Distribution of liquid crystal (LC) molecules in the TN cell is characterized using transmission ellipsometry. The retardation of the rubbed PI surface increases as rubbing strength increases. The tilt angle of the optic axis of the rubbed PI surface decreases as rubbing strength especially as the angular speed of the rubbing roller increases. Pretilt angle of LC molecules in the TN cell shows strong correlation with tilt angle of the optic axis of the rubbed PI surface. Both the apparent order parameter and the effective twist angle of the LC molecules in the TN cell decrease as the pretilt angle of LC molecules increases.
Keywords
Rubbed polyimide; Optical anisotropy; Distribution of liquid crystal; Ellipsometry;
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Times Cited By KSCI : 7  (Citation Analysis)
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1 S. Patari, T. K. Devi, and A. Nath, "Studies of optical texture, birefringence, order parameter, normalized polarizability and validation of the four-parameter model of a thermotropic mesogen 7OAOB," J. Mol. Liq. 215, 244-252 (2016).   DOI
2 M. F. Vuks, "Determination of the optical anisotropy of aromatic molecules from the double refraction of crystals," Opt. Spectrosc. 20, 361-364 (1966).
3 A. Kanwar, "Measurement of order parameter, birefringence and polarizability of liquid crystals," J. Opt. 42, 311-315 (2013).   DOI
4 S. Y. Kim, "The explicitly quasi-linear relation between the order parameter and normalized birefringence of aligned uniaxially anisotropic molecules determined using a numerical method," Korean J. Opt. Photon. 27, 223 (2016).   DOI
5 S. Y. Kim, "Universality of the quasi-linear relation between the order parameter and the normalized birefringence of aligned uniaxially anisotropic molecules," Korean J. Opt. Photon. 28, 33 (2017).   DOI
6 J. W. Ryu and S. Y. Kim, "Determination of the optic axis distribution of a hybridly aligned discotic material for wide-view films," J. Kor. Phys. Soc. 57, 233-239 (2010).   DOI
7 S. Y. Kim, Ellipsometry (Ajou University Press, Korea, 2000), Chapter 3-4.
8 H. Fujiwara, Spectroscopic ellipsometry: principles and applications (John Wiley & Sons, Ltd., Japan, 2007).
9 S. Y. Kim, "Ellipsometric expressions of multilayered substrate coated with a uniaxially anisotropic alignment layer," Korean J. Opt. Photon. 24, 271-278 (2013).   DOI
10 S. Y. Kim, "Ellipsometric expressions for a sample coated with uniaxially anisotropic layers," Korean J. Opt. Photon. 26, 275-282 (2015).   DOI
11 S. Y. Cho, S. U. Park, and S. Y. Kim, "Quantitative characterization of optical anisotropy of rubbed polyimide alignment layers in relation with distribution of liquid crystal molecules using an improved reflection ellipsometer," in Proc. 7th International Conference on Spectroscopic Ellipsometry (Germany, Jun. 2016), p. 322.
12 S. Y. Cho, S. U. Park, S. M. Yang, and S. Y. Kim, "Ellipsometric characterization of the surface of rubbed polyimide and distribution of liquid crystal molecules in TN cells," in Proc. 23rd International Display Workshops in Conjunction with Asia Display (Japan, Dec. 2016), pp. 159-161.
13 P. G. de Gennes, "Short range order effects in the isotropic phase of nematics and cholesterics," Mol. Cryst. Liq. Cryst. 12, 193-214 (1971).   DOI
14 K. H. Lyum, S. U. Park, S. M. Yang, H. K. Yoon, and S. Y. Kim, "Precise measurement of ultra small retardation of LCD alignment layer using improved transmission ellipsometry," Korean J. Opt. Photon. 24, 77-85 (2013).   DOI
15 V. G. K. M. Pisipati, D. Madhavi Latha, P. V. Datta Prasad, and G. Padmaja Rani, "Order parameter studies from effective order geometry in a number of liquid crystals of different homologous series," J. Mol. Liq. 174, 1-4 (2012).   DOI
16 J. J. Ge, C. Y. Li, G. Xue, I. K. Mann, D. Zhang, S.-Y. Wang, F. W. Harris, S. Z. D. Cheng, S.-C. Hong, X. Zhuang, and Y. R. Shen, "Rubbing-induced molecular reorientation on an alignment surface of an aromatic polyimide containing cyanobiphenyl side chains," J. Am. Chem. Soc. 123, 5768- 5776 (2001).   DOI
17 D. S. Seo, K. Araya, N. Yoshida, M. Nishikawa, Y. Yabe, and S. Kobayashi, "Effect of the polymer tlit angle for generation of pretilt angle in nematic liquid crystal on rubbed polyimide surfaces," Jpn. J. Appl. Phys. 34, 503-506 (1995).   DOI
18 K. H. Lyum, H. K. Yoon, S. J. Kim, S. H. An, and S. Y. Kim, "Study of ultra-small optical anisotropy profile of rubbed polyimide film by using transmission ellipsometry," J. Opt. Soc. Korea 18, 156-161 (2014).   DOI
19 J. H. Lee, M. S. Park, S. M. Yang, S. U. Park, M. H. Lee, and S. Y. Kim, "Precise measurement of the ultrasmall optical anisotropy of rubbed polyimide using an improved reflection ellipsometer," Korean J. Opt. Photon. 26, 195-202 (2015).   DOI
20 M. S. Park, S. M. Yang, S. U. Park, and S. Y. Kim, "Quantitative characterization of uniaxial anisotropy of rubbed polyimide alignment layer using reflection ellipsometry," in Proc. 22nd International Display Workshops (Japan, Dec. 2015), pp. 68-69.
21 Retrieved from the world wide web; http://www.ellipsotech.com/Ellipsometer.html.
22 N. A. J. M. van Aerle, M. Barmentlo, and R. W. J. Hollering, "Effect of rubbing on the molecular orientation within polyimide orienting layers of liquid-crystal displays," J. Appl. Phys. 74, 3111-3120 (1993).   DOI
23 J. W. Ryu, Study on the non-uniform distribution of anisotropy in wide view film using ellipsometry, Ph.D. Dissertation, Ajou University, 36-113 (2010).
24 L. A. Goodman, J. T. McGinn, C. H. Anderson, and F. DiGeronimo, "Topography of obliquely evaporated silicon oxide films and its effect on liquid-crystal orientation," IEEE Trans. Electron Devices 24, 795-804 (1977).   DOI
25 G. Roberts, Langmuir-Blodgett Films (Springer Science & Business Media, 2013), Chapter 7.
26 Y. Sato, K. Sato, and T. Uchida, "Relationship between rubbing strength and surface anchoring of nematic liquid crystal," Jpn. J. Appl. Phys. 31, L579 (1992).   DOI
27 A. J. Pidduck, G. P. Bryan-Brown, S. Haslam, R. Bannister, I. Kitely, T. J. McMaster, and L. Boogaard, "Atomic force microscopy studies of rubbed polyimide surfaces used for liquid crystal alignment," J. Vac. Sci. Tech. A 14, 1723-1728 (1996).   DOI
28 I. Hirosawa, "Method of characterizing rubbed polyimide film for liquid crystal display devices using reflection ellipsometry," Jpn. J. Appl. Phys. 35, 5873-5875 (1996).   DOI
29 I. Hirosawa, H. Miyairi, T. Matsushita, and S. Saito, "The relation between pretilt angle of liquid crystal and optical anisotropy of alignment layer," Mol. Cryst. and Liq. Cryst. 368, 565-571 (2001).   DOI
30 T. Sakai, K. Ishikawa, H. Takezoe, N. Matsuie, Y. Yamamoto, H. Ishii, Y. Ouchi, H. Oji, and K. Seki, "Surface orientation of main and side chains of polyimide alignment layer studied by near-edge X-ray absorption fine structure spectroscopy," J. Phys. Chem. B 105, 9191-9195 (2001).   DOI
31 B. Jerome, "Surface effects and anchoring in liquid crystals," Rep. Prog. Phys. 54, 391 (1991).   DOI
32 P. Yeh and C. Gu, Optics of liquid crystal displays (John Wiley & Sons, Inc., New York, 2010), Chapter 2.
33 M. Jiao, Z. Ge, Q. Song, and S. T. Wu, "Alignment layer effects on thin liquid crystal cells," Appl. Phys. Lett. 92, 061102 (2008).   DOI
34 K. Ichimura, Y. Suzuki, T. Seki, Y. Kawanishi, and K. Aoki, "Reversible alignment change of liquid crystals induced by photochromic molecular films, 2. Reversible alignment change of a nematic liquid crystal induced by pendent azobenzene groups-containing polymer thin films," Makromol. Chem., Rapid Commun. 10, 5-8 (1989).   DOI
35 K. Ichimura, "Photoalignment of liquid-crystal systems," Chem. Rev. 100, 1847-1874 (2000).   DOI