Molecular Alignment on Polymide Film for Liquid Crystals by the Application of Photolithography

Abstract

In this study, the photolithographic technique for molecular alignment on the polyimide thin film was studied. The liquid crystal alignment properties of the photolithographic application were presented by the polyimide thin films and observed on photoaligned polyimide film by a surface profiler. This method was provided by the micropatterning process that includes spin-coating, UV exposing and wet chemical etching. The cell gap of liquid crystal displays was measured by the rotational scanning interferometer unit. The results of the photolithographic method and the molecular alignment properties of the nematic liquid crystal cell were observed by applying an electric field with the micro-patterning interval of approximately 100 microns. These results will be developed gradually in further studies for nano-scale applications.

Keywords

• Liquid crystals,polyimide thin films,photolithography,molecular alignment

References

1. [1] P. Slikkerveer, P. Bouten, P. Cirkel, J. de Goede, H. Jagt, N. Kooyman, G. Nisato, R. van Rijswijk and P. Duineveld, 16.2: A fully flexible colour display, SID Symposium Digest of Technical Papers 35 (2004), 770–773.
2. [2] S. Varghese, S. Narayanankutty, C. W. M. Bastiaansen, G. P. Crawford and D. J. Broer, Patterned alignment of liquid crystals by µ-rubbing, Advanced Materials 16 (2004), 1600–1605.
3. [3] J. Osterman, C. Ad˚as, L. Madsen and K. Skarp, P-124: Properties of azo-dye alignment layer on plastic substrates, SID Symposium Digest of Technical Papers 36 (2005), 772–775.
4. [4] V. Konovalov, V. Chigrinov, H. S. Kwok, H. Takada and H. Takatsu, Photoaligned vertical aligned nematic mode in liquid crystals, Japanese Journal of Applied Physics 43 (2004), 261–266.
5. [5] V. G. Chigrinov, Liquid Crystal Devices: Physics and Applications, Artech House, Boston 1999.
6. [6] M. O’Neill and S. M. Kelly, Photoinduced surface alignment for liquid crystal displays, Journal of Physics D: Applied Physics 33 (2000), R67.
7. [7] M. Schadt, H. Seiberle and A. Schuster, Optical patterning of multi-domain liquid-crystal displays with wide viewing angles, Nature 381 (1996), 212–215.
8. [8] R. Yamaguchi, Y. Goto and S. Sato, A novel patterning method of liquid crystal alignment by azimuthal anchoring control, Japanese Journal of Applied Physics 41 (2002), L889–L891.

9. [9] R. Karapinar, M. O’Neill, S. M. Kelly, A. W. Hall and G. J. Owen, Molecular alignment of liquid crystals on a photosensitive polymer surface exposed to linearly polarised ultraviolet laser radiation, ARI - An International Journal for Physical and Engineering Sciences 51 (1998), 61–65.
10. [10] G.-D. Lee, T.-H. Yoon and J. C. Kim, Cell gap measurement method for single-polarizer reflective liquid crystal cells, Japanese Journal of Applied Physics 40 (2001), 3330–3331.
11. [11] S.-T. Wu and G. Xu, Cell gap and twist angle determinations of a reflective liquid crystal display, IEEE Transactions on Electron Devices 47 (2000), 2290–2293.
12. [12] X. Zhu, W.-K. Choi and S.-T. Wu, A simple method for measuring the cell gap of a reflective twisted nematic LCD, IEEE Transactions on Electron Devices 49 (2002), 1863–1867.
13. [13] H. L. Ong, 26.1: Simple and accurate optical reflection and phase compensation methods for reflective LCD cell gap, SID Symposium Digest of Technical Papers 32 (2001), 430–433.
14. [14] S. J. Hwang, S.-T. Lin, C.-H. Lai, A novel method to measure the cell gap and pretilt angle of a reflective liquid crystal display, Optics Communications 260 (2006), 614–620.
15. [15] H. J. Deuling, Deformation of nematic liquid crystals in an electric field, Molecular Crystals and Liquid Crystals 19 (1972), 123–131.
16. [16] J. Osterman, Investigations of Optical Properties and Photo-Alignment in Bistable Nematic Liquid Crystal Displays, PhD. Thesis, Upsala University, Uppsala 2005.
17. [17] V. Vorflusev, H.-S. Kitzerow and V. Chigrinov, Azimuthal anchoring energy in photoinduced anisotropic films, Japanese Journal of Applied Physics 34 (1995), L1137–L1140.
18. [18] H. Yokoyama and R. Sun, Simplified high-electric-field technique for measuring the liquid crystal anchoring strength, Japanese Journal of Applied Physics 39 (2000), L45–L47.
19. [19] Y.-F. Lin, M.-C. Tsou and R.-P. Pan, Alignment of liquid crystals by ion etched grooved glass surfaces, Chinese Journal of Physics 43 (2005), 1066–1073.
20. [20] H. Hah, S.-J. Sung, M. Han, S. Lee and J.-K. Park, Effect of the shape of imprinted alignment layer on the molecular orientation of liquid crystal, Materials Science and Engineering: C 27 (2007), 798–801.