Films birefringence

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

The clarity of a translucent crystalline polymer, such as polypropylene (PP), may be improved by biaxial orientation. Monoaxial orientation of a crystalline film produces an anisotropic birefringent film. 

Retardation matching Control of birefringence Film elongation... 

As in the case of low-molecular liquid crystals the majority of information about the structure of LC polymers is obtained from their optical textures and X-ray diffraction data. Because of high viscosity of polymer melts, which results in retardation of all structural and relaxation processes it is quite difficult to obtain characteristic textures for LC polymers. As is noted by the majority of investigators smectic LC polymers form strongly birefringent films as well from solutions, as from melts11 27-... 

Figure 6. The guided mode dispersion curves for a birefringent film and an optically isotropic substrate. Both the fundamental and harmonic curves are shown. The TE mode utilizes the ordinary refractive index and TM primarily the extraordinary index. Note the change in horizontal axis needed to plot both the fundamental and harmonic dispersion curves. Phase-matching of the TEq(co) to the TMo(2o>) is obtained at the intersection of the appropriate fundamental and harmonic curves.

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. 

Interference between the e-ray and the o-ray, which have travelled with different velocity through the nematic medium, gives rise to the coloured appearance of LCDs operating with plane polarised light. For a wave at normal incidence, the phase difference in radians between the o-ray and the e-ray caused by traversing a birefringent film of thickness d and birefringence An, is referred to as the optical retardation, <5 ... 

Horowitz F, Mendes SB (1994) Envelope and wave-guide methods - a comparative-study of PbE2 and Ce02 birefringent films. Appl Opt 33(13) 2659-2663... 

The unisotropic columnar microstructure of many films strongly suggests that they should be birefringent. Films evaporated at normal incidence are expected to be uniaxial birefringence with optic axis normal to the plane of vapour incident... 

Yu, H. F. Kobayasi, T. (2009b). Fabrication of Stable Nanocylinder Arrays in Fiighly Birefringent Films of an Amphiphilic Liquid-Crystalline Diblock Copolymer. ACS Appl Mater. Interfaces, 2009,1, 2755-2762. 

Figure 3.1 Schematic diagram showing a light beam propagating through a uniaxial birefringent film.

The polarization of a light beam can be changed into any other polarization state by using a proper birefringent film. If the incident light is linearly polarized along the x axis and the uniaxial birefringent film is a quarter plate with its slow axis (the uniaxial axis) at 45° with... 

If the birefringent film is sandwiched between two polarizers with the transmission... 

Birefringent films are used as compensation films to improve the viewing angle of hquid crystal displays. They can be divided into three groups according to the orientation of the uniaxis (c axis) with respect to the normal of the film. 

In the same way that the Jones matrix can be used to numerically calculate the optical properties of non-uniform birefringence film, the MeuUer matrix can be used to numerically calculate the optical properties of a non-uniform birefidngence film. We divide the film into N slabs as shown... 

Uniaxial film is an anisotropic birefringent film with only one optical axis. For simplicity, let us limit our discussions to non-absorption uniaxial films. From the viewpoint of optical axis orientation, uniaxial films can be classified into a film and c film. An a film s optical axis is parallel to the film surface, while a c film s optical axis is perpendicular to the film surface. 

When the focal conic groups are well aligned (homeogeneous alignment, Sec. 3.1) and viewed between crossed polarizers, a fairly uniform birefringent film is seen, and upon applying a voltage the film appears black (Fig. 7). Dichroic dyes can be added to the smectic phase and a contrast between colored (focal conic) and clear (homeotrop-ic) produced [55]. 

Here n (n denotes the fast and slow indices (for anisotropic materials with rod-shaped molecules n = n and = nj, d is the thickness of the birefringent film, and A is the wavelength of the light. The component that feels larger refractive index will be slower, i.e., retarded with respect to the other polarization directions. 

If the optical axis of the birefringent film makes an angle (j) with x, we can express the Jones matrix as ... 

Michad-Levi chart for estimating the birefringence of a birefringent film of known thickness. 

---