Hybrid anchoring for a color-reflective dual- frequency cholesteric liquid crystal device switched by low voltages
چکیده
Cholesteric liquid crystal (CLC) materials used in electro-optical (EO) devices are characterized by high operating voltage and slow response speed, which hinders their further development in display applications. Dual-frequency CLCs (DFCLCs) can solve the problem of slow bistable transition, but the operating voltage is still high, especially in color-reflective DFCLC cells. Here we report a simple approach to lowering the switching voltage as well as to shortening the response time. This technique adopts hybrid surface treatment to modulate the structural arrangement of CLC molecules. Both planarand vertical-alignment layers are employed and coated on one and the other substrates separately to improve the electro-optical properties of DFCLCs. We show that the threshold voltage for switching can be decreased to as low as 5 V and the shortest response time is measured to be 0.8 ms, which renders CLC EO devices including displays more practical for commercial purpose. ©2015 Optical Society of America OCIS codes: (160.3710) Liquid crystals; (160.1585) Chiral media; (230.2090) Electro-optical devices; (230.3720) Liquid-crystal devices. References and links 1. X.-Y. Huang, D.-K. Yang, and J. W. Doane, “Transient dielectric study of bistable reflective cholesteric displays and design of rapid drive scheme,” Appl. Phys. Lett. 67(9), 1211–1213 (1995). 2. D.-K. Yang, J.-W. Doane, Z. Yaniv, and J. Glasser, “Cholesteric reflective display: drive scheme and contrast,” Appl. Phys. Lett. 64(15), 1905–1907 (1994). 3. S.-T. Wu and D.-K. Yang, Reflective Liquid Crystal Displays (Wiley, 2001), Ch. 8 4. P.-T. Lin, X. Liang, H. Ren, and S.-T. Wu, “Tunable diffraction grating using ultraviolet-light-induced spatial phase modulation in dual-frequency liquid crystal,” Appl. Phys. Lett. 85(7), 1131–1133 (2004). 5. Y. Yin, S. V. Shiyanovskii, A. B. Golovin, and O. D. Lavrentovich, “Dielectric torque and orientation dynamics of liquid crystals with dielectric dispersion,” Phys. Rev. Lett. 95(8), 087801 (2005). 6. Y.-C. Hsiao, C.-Y. Tang, and W. Lee, “Fast-switching bistable cholesteric intensity modulator,” Opt. Express 19(10), 9744–9749 (2011). 7. I. I. Smalyukh, B. I. Senyuk, P. Palffy-Muhoray, and O. D. Lavrentovich, “Electric-field-induced nematiccholesteric transition and three-dimensional director structures in homeotropic cells,” Phys. Rev. E 72(6), 061707 (2005). 8. D. Subacius, P. J. Bos, and O. D. Lavrentovich, “Switchable diffractive cholesteric gratings,” Appl. Phys. Lett. 71(10), 1350–1352 (1995). 9. I. Gvozdovskyy, O. Yaroshchuk, M. Serbina, and R. Yamaguchi, “Photoinduced helical inversion in cholesteric liquid crystal cells with homeotropic anchoring,” Opt. Express 20(4), 3499–3508 (2012). 10. M. R. Lewis and M. C. K. Wiltshire, “Hybrid aligned cholesteric: A novel liquid-crystal alignment,” Appl. Phys. Lett. 51(15), 1197–1199 (1987). 11. Y.-C. Hsiao, C.-Y. Wu, C.-H. Chen, V. Ya. Zyryanov, and W. Lee, “Electro-optical device based on photonic structure with a dual-frequency cholesteric liquid crystal,” Opt. Lett. 36(14), 2632–2634 (2011). 12. Y.-C. Hsiao, H.-T. Wang, and W. Lee, “Thermodielectric generation of defect modes in a photonic liquid crystal,” Opt. Express 22(3), 3593–3599 (2014). 13. Y.-C. Hsiao, C.-T. Hou, V. Ya. Zyryanov, and W. Lee, “Multichannel photonic devices based on tristable polymer-stabilized cholesteric textures,” Opt. Express 19(24), 23952–23957 (2011). 14. Y.-C. Hsiao, Y.-H. Zou, I. V. Timofeev, V. Ya. Zyryanov, and W. Lee, “Spectral modulation of a bistable liquid-crystal photonic structure by the polarization effect,” Opt. Mater. Express 3(6), 821–828 (2013). 15. F.-C. Lin and W. Lee, “Color-reflective dual-frequency cholesteric liquid crystal displays and their drive schemes,” Appl. Phys. Express 4(11), 112201 (2011). 16. Y.-C. Hsiao and W. Lee, “Lower operation voltage in dual-frequency cholesteric liquid crystals based on the thermodielectric effect,” Opt. Express 21(20), 23927–23933 (2013). 17. S.-Y. Lu and L.-C. Chien, “A polymer-stabilized single-layer color cholesteric liquid crystal display with anisotropic reflection,” Appl. Phys. Lett. 91(13), 131119 (2007).