Liquid crystal display cholesteric displays

B.-G. Wu, J. Gao, Y.D. Ma, V. Zhou, and R.B. Timmons, Zero held, multistable cholesteric liquid crystal displays. International Display Research Conference 94, pp. 476-479, 1994. 

X.-Y. Huang, A. Khan, D. Davis, C. Jones, N. Miller, and J.W. Doane, Full color (4096 colors) reflective cholesteric liquid crystal display, Asia Display 98, 883-886 (1998). 

Thermotropic cholesterics have several practical applications, some of which are very widespread. Most of the liquid crystal displays produced use either the twisted nematic (see Figure 7.3) or the supertwisted nematic electrooptical effects.6 The liquid crystal materials used in these cells contain a chiral component (effectively a cholesteric phase) which determines the twisting direction. Cholesteric LCs can also be used for storage displays utilizing the dynamic scattering mode.7 Short-pitch cholesterics with temperature-dependent selective reflection in the visible region show different colors at different temperatures and are used for popular digital thermometers.8... 

Nematic gels are very interesting systems, thus deserving further study. Actually, these systems are being studied experimentally for applications. Examples are polymer dispersed liquid crystal displays are sometimes dispersed not in a polymer, but in a polymer network. Displays by means of the polymer stabilized cholesteric texture change, are also achieved in crosslinked systems. In addition, the chiral smectic phase has been obtained in such systems as well. Other types of liquid crystal gels have been applied or are expected to be applied in such devices. 

I. Dozov, A. Boissier and T. Laboureau, Nemoptic s bistable nematic liquid-crystal technology - Cholesterics or ferroelectrics are not necessary to make a bistable LCD, and using conventional nematics offers some substantial advantages, Information Display 18(1), 10 13, (2002). 

Kent Display is a pioneer of cholesteric liquid crystal displays (ChLCDs) in which the director of the liquid crystal twists around a helical axis [3]. The remarkable property is that the cholesteric material reflects light of certain wavelengths depending on the pitch over which the director rotates. When an electric held is applied. 

The method to manufacture cost-effective displays is to use proper processes for mass production or on a large scale. One example is a roll-to-roll process which needs a flexible substrate to be coated or printed display materials. Here, an important issue is to provide a monolayer of display materials. In order to supply this mono-layer, a variety of methods have been tried for encapsulated cholesteric liquid crystals by Kent Display, microencapsulated electrophoretic... 

Chari K, Rankin M, Johnson DM, Blanton TN, Capurso RG (2006) Single-substrate cholesteric liquid crystal displays by colloidal self-assembly. Appl Phys Lett 88 043502... 

Reflective cholesteric liquid crystal display has drawn much attention as an ideal flat portable panel display device due to its low power consumption. PPy film with a thickness of about 4 pm was spin-coated on a glass substrate. The PPy layer, opaque to light but very reflective, acted as a lightabsorbing layer as well as the electrode in the device (Figure 8.46) [86]. The initial reflectance of the... 

D. W. Berreman and W. R. Heffner, New bistable cholesteric liquid-crystal display, Appl. Phys. Lett., 37, 109 (1980). 

D. Davis, K. Hoke, A. Khan, et al., Multiple color high resolution reflective cholesteric liquid crystal displays, Proc. Intnl. Display Research Conf, 242 (1997). 

P. Watson, J. E. Anderson, V. Sergan, and P. J. Bos, The transition mechanism of the transient planar to planar director configuration change in cholesteric liquid crystal displays, Liq. Cryst., 26, 1307 (1999). 

The majority of current commercial liquid crystal displays are based on the twisted nematic electrooptic effect using active matrices to give, for example, complex computer lap-top screens [13]. It is often overlooked that these displays are based on long pitch chiral nematic materials to remove so-called reverse twist, and the original papers [254, 255] referred to the effect as a positive planar cholesteric to nematic phase... 

Hughes, C. J. Coates, D. AUdns, A. O. Cholesteric liquid crystal display device. PCT Int. Appl. WO... 

Wu, S.-T., Yang, D.-K. Reflective Liquid Crystal Displays. Wiley, New York (2001) Yang, D.-K., Huang, X.-Y., Zhu, Y.-M. Bistable cholesteric reflective displays materials and drive schemes. Annu. Rev. Mater. Sci. 27, 117-146 (1997)... 

J. W. Doan and A. Khan, Cholesteric liquid crystals for flexible displays. In Flexible Flat Panel Displays, Ed. G. P. Crawford, John WUey Sons, Ltd, Chichester (2005), 331-354. 

By far the most important commercial applications of nematic liquid crystals are in the a multi-billion dollar display industry. Cholesteric, or chiral nematic liquid crystals have been used in coloured guest-host displays and in thermography/ther-mochromic applications. 

Electronic displays make use of the fact that the orientation of the molecules in liquid crystals changes in the presence of an electric field. This reorientation causes a change in their optical properties, making them opaque or transparent, and hence forming a pattern on a screen. Cholesteric liquid crystals are also of interest because the helical structure unwinds slightly as the temperature is changed. Because the twist of the helical structure affects the optical properties of the liquid crystal, these... 

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