Negative dispersion retarder using two negative birefringence films Anoop Kumar Srivastava, Seungbin Yang, and Ji-Hoon Lee* Advanced Electronics and Information Research Center, Division of Electronics Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756, South Korea *
[email protected]
Abstract: The achromatic response and wide viewing angle for varying wavelength of incident light are of long waiting research to be utilized it for the display devices. Such response can be obtained by employing the retarder that exhibits negative birefringence and negative dispersion. In this paper, negative dispersion half-wave retarder and negative dispersion quarter-wave retarder have been demonstrated by optimizing the retardation and the angle between the extraordinary axes of polystyrene and polymethylmethacrylate films. The optimum angles for half and quarter-wave retarders were found to be 40° and 70°, respectively for different retardation values of polystyrene and poly-methylmethacrylate films. ©2015 Optical Society of America OCIS codes: (160.1190) Anisotropic optical materials; (160.3710) Liquid crystals
References and links 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.
S. Pancharatnam, “Achromatic combinations of birefringent plates. Part I. An achromatic circular polarizer,” Proc. - Indian Acad. Sci., Sect. A 41, 130–136 (1955). D. Clarke, “Achromatic halfwave plates and linear polarization rotators,” Opt. Acta (Lond.) 14(4), 343–350 (1967). P. Hariharan, “Achromatic and apochromatic half wave and quarter wave retarders,” Opt. Eng. 35(11), 3335– 3337 (1996). Y.-C. Yang and D.-K. Yang, “Achromatic reduction of off-axis light leakage in LCDs by self-compensated phase retardation (SPR) film,” Proc. SID Digest 1955–1958 (2008). S. Shen, J. She, and T. Tao, “Optimal design of achromatic true zero-order waveplates using twisted nematic liquid crystal,” J. Opt. Soc. Am. A 22(5), 961–965 (2005). T.-H. Yoon, G.-D. Lee, and J. C. Kim, “Nontwist quarter-wave liquid-crystal cell for a high-contrast reflective display,” Opt. Lett. 25(20), 1547–1549 (2000). S.-W. Oh and T.-H. Yoon, “Elimination of light leakage over the entire viewing cone in a homogeneouslyaligned liquid crystal cell,” Opt. Express 22(5), 5808–5817 (2014). R. K. Komanduri, K. F. Lawler, and M. J. Escuti, “Multi-twist retarders: broadband retardation control using self-aligning reactive liquid crystal layers,” Opt. Express 21(1), 404–420 (2013). A. Uchiyama and T. Yatabe, “Control of wavelength dispersion of birefringence for oriented copolycarbonate films containing positive and negative birefreingent units,” Jpn. J. Appl. Phys. 42(11), 6941–6945 (2003). A. Uchiyama, Y. Ono, Y. Ikeda, H. Shuto, and K. Yahata, “Copolycarbonate optical films developed using birefringence dispersion control,” Polym. J. 44(10), 995–1008 (2012). K. Kuboyama, T. Kuroda, and T. Ougizawa, “Control of wavelength dispersion of birefringence by miscible polymer blends,” Macromol. Symp. 249-250(1), 641–646 (2007). O. Parri, G. Smith, R. Harding, H.-J. Yoon, I. Gardiner, J. Sargent, and K. Skjonnemand, “Patterned retarder films using reactive mesogen technology,” Proc. SPIE 7956, 79560W (2011). H. Lee and J.-H. Lee, “Negative dispersion of birefringence in two-dimensionally self-organized smectic liquid crystal and monomer thin film,” Opt. Lett. 39(17), 5146–5149 (2014). S. Yang, H. Lee, and J.-H. Lee, “Negative dispersion of birefringence of smectic liquid crystal-polymer composite: dependence on the constituent molecules and temperature,” Opt. Express 23(3), 2466–2471 (2015). H. Lee, S. Yang, and J.-H. Lee, “Electro-optical properties of smectic liquid crystal-polymer composite with negative dispersion of birefringence,” Curr. Appl. Phys. 15(4), 456–460 (2015). P. Yeh and C. Gu, Optics of Liquid Crystal Displays, 2nd edi. (John Wiley & Sons, 2010) Chap. 4, Chap. 6. T. Kojo, A. Tagaya, and Y. Koike, “Mechanism of generation of birefringence in poly(methylmethacrylate/styrene),” Polym. J. 44(2), 167–173 (2012).
#236765 - $15.00 USD © 2015 OSA
Received 24 Mar 2015; revised 27 Apr 2015; accepted 4 May 2015; published 8 May 2015 18 May 2015 | Vol. 23, No. 10 | DOI:10.1364/OE.23.013108 | OPTICS EXPRESS 13108
1. Introduction Generally, the phase retardation Г≡2πΔnd/λ of the natural birefringent materials decreases with longer λ, called as positive dispersion (PD) of birefringence. Here, Δn is defined as ne-no, where ne and no are the extraordinary and ordinary refractive index, respectively, and d is the thickness of the film. The PD medium also shows a decrease of Re(λ)≡Δnd with longer λ and this limits the bandwidth of the compensation film. There have been many efforts to make a retarder with negative dispersion (ND) of birefringence whose birefringence or Re(λ) get increased with longer λ [1–4]. The ND retarder has a wider bandwidth than PD retarder, thus can be an achromatic retarder with constant phase retardation over the wide range of λ. The well-known method to obtain the ND retarder is stacking PD retarders with different dispersion property of Re(λ) [1–6]. Multilayers of twist-oriented reactive mesogen have been also reported to show ND of birefringence [7,8]. Recently, single layer approaches using copolymers [9–11], biaxial reactive mesogens [12], and smectic liquid crystal-polymer composites have been developed [13–15]. Further, all previous ND retarders have been made of positive birefringence (PB) materials [16]. The PB medium means a substance showing ne>no, thus giving a positive sign of Δn. With this reason, the Rth value defined as [(nx + ny)/2-nz]d was always positive, where nx and ny are the in-plane refractive indices of the retarder and nz is the refractive index to the surface normal direction. To minimize the viewing angle dependence of the liquid crystal display (LCD) devices, the Rth value should be zero and this can be realized provided nz = (nxny)1/2 [16]. Since most of the liquid crystal displays (LCDs) use the liquid crystal (LC) with PB property, the Rth value of the LC layer is positive. Thus, to make the Rth of the LCD to be zero, the Rth value of the compensation film should negative. This can be satisfied by using a retarder which have negative birefringence (NB), ne