Birefringence displays

Figure 13b shows a similar scan but across a line of lOO-jjim width, displaying a pipe birefringence obtained for a more concentrated solution (0.2%). The pipe birefringence displays a clear dip in the velocity along the axis of the jet system where the dark line is seen in the image. Such effects were previously observed by Lyazid et al (43). This solution corresponds closely to the pipe region of the phase diagram shown in Figure 12. Visually the appearance is similar to Figure lOd for PEO.

Thus it passes through the top polariser and the cell appears bright. Because the switching in both directions is driven by the interaction of the spontaneous polarisation with the electric field (rather than the interaction between an induced polarisation and the electric field or a relaxation process when the electric field is removed), these surface stabilised ferroelectric hquid crystal (SSFLC) displays are much faster than twisted nematic and birefringent displays. 

Scheffer T J, Nehring J, Kaufmann M, Amstutz H, Heimgartner D and Eglin P 1985 24 80 character LCD panel using the supertwisted birefringence effect Dig. Tech. Papers Int. Symp. Soc. Information Display 16 120-3... 

Figure 17 Isothermal melting of Ziegler-Natta isotactic poly(propylene). (a) Spherulites with mixed birefringence at Tc = 148°C. The top middle figure displays the melting for the same thermal history, (b) Subsequent to crystallization, the temperature was raised to 171°C spherulites acquire negative birefringence, (c), (d) and (e) Isothermal melting at 171°C for 80, 200 and 300 min, respectively. Reproduced with permission from W.T. Huang, Dissertation, Florida State University, 2005. (See Color Plate Section at the end of this book.)...

Switchable birefringence film Supertwisted nematic (STN), ferroelectric (FLC), electrically controlled birefringence (ECB) displays... 

Physical properties of liquid crystals are generally anisotropic (see, for example, du Jeu, 1980). The anisotropic physical properties that are relevant to display devices are refractive index, dielectric permittivity and orientational elasticity (Raynes, 1983). A nematic LC has two principal refractive indices, Un and measured parallel and perpendicular to the nematic director respectively. The birefringence An = ny — rij is positive, typically around 0.25. The anisotropy in the dielectric permittivity which is given by As = II — Sj is the driving force for most electrooptic effects in LCs. The electric contribution to the free energy contains a term that depends on the angle between the director n and the electric field E and is given by... 

Biaxially oriented films such as PET and PEN are birefringent. For LC displays which depend on light of known polarization this means that birefringent films, which would change the polarization state, are unlikely to be used as substrates. Films based on amorphous polymer are not birefringent and are more suitable for LC displays. Birefringence is not an issue with OLED, electrophoretic displays, or, indeed, some LC displays. 

Up to now, only two sets of data of the osmotic coefficient of rod-like polyelectrolytes in salt-free solution are available 1) Measurements by Auer and Alexandrowicz [68] on aqueous DNA-solutions, and 2) Measurements of polyelectrolyte PPP-1 in aqueous solution [58]. A critical comparison of these data with the PB-cell model and the theories delineated in Sect. 2.2 has been given recently [59]. Here it suffices to discuss the main results of this analysis displayed in Fig. 8. It should be noted that the measurements by the electric birefringence discussed in Sect. 4.1 are the most important prerequisite of this analysis. These data have shown that PPP-1 form a molecularly disperse solution in water and the analysis can therefore assume single rods dispersed in solution [49]. 

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