Optical compensation

Optical compensation for polymers with chiral monomeric units may also occur when the racemic polymer consists of crystallites, each composed only of the rectus chains or only of the sinister polymer chains, and a same amount of optical antipode crystallites is present. This intercrystallite optical compensation211 has been found, for instance, in isotactic poly(propylene sulfide),212 poly ((3 -methy lpropiol ac (one),213 and poly(isopropylethylene oxide),214 where isochiral 2/1 helical chains are included in orthorhombic unit cells according to the space group P2 2 2. ... 

The standard curve will in some instances not follow a straight course or will have a wrong slope. If the slope is too steep, i.e., if the double concentration gives more than double a value of optical density, one will suspect the presence of an inhibitor or toxic factor, relatively more effective at lower concentrations, or of a stimulating factor relatively more effective at higher concentrations. In the case of strongly colored samples, optical compensation can be achieved in the reading of the... 

More sophisticated optical compensation layers can be produced as anisotropic networks from reactive mesogens (liquid crystals) in a macroscopically... 

Note A separate set of windows, both for the iimer cell and for the water jacket, should be available for optical compensation as indicated above. 

In the laboratories of BASF (Badische Anilin- and Soda-Fabrik) at Ludwigshafen, the importance of infrared spectroscopy for industrial purposes was realized as early as the 1930 s. The first IR instrument with a modulated beam was built by Lehrer in 1937 and modified to a double beam instrument with optical compensation in 1942. Luft described the first non-dispersive infrared analyzer in 1943. He used the gas to be analyzed as absorber in a photo-acoustic detector cell. Thus, the instrument was sensitive only to this gas. He also provided a survey of early industrial applications of infrared spectroscopy (Luft, 1947). 

The correctness of Natta s view was shown by Veerkamp and Veer-mans (92) who determined the intensities of the absorptions occurring in C2-C3 copolymers at 13.64 and 13.85 p by using an optical compensation technique from the resulting data they derived the distribution of the CH2 groups over sequences of 3 and 5 or more CH2 groups as a function of C3 incorporation. 

In addition, the crystal structures of both the racemic copolyamidc 11.7 and the cquimolccular mixture of the two configurationally homogeneous d- and i.-polyamides were studied and compared with that of optically pure 110.93 This study combined X-ray. electron microscopy, and 13C CP-MAS NMR measurements with computational methods. The two optically compensated and the optically pure polymers were shown to be highly crystalline systems the melting point of the racemic mixture was 250°C, considerably higher than those of the homopolymer (232°C) and the racemic polymer (226°C). The crystal structure of the racemic mixture could be... 

Fourier Transform Infrared Spectroscopy.—New Fourier transform (FT) spectrometers recently described in the literature include a double-beam optically compensated spectrometer suitable for weak i.r. absorptions (0.5—1%) and a... 

A series of other examples are given in the literature. " The method of preparation of the optical compensation film has been described in detail... 

K. Matsuoka and K. Kawata. Optical compensation sheet, liquid crystal display device, and liquid crystal composition. US Patent 6444280, assigned to Fuji Photo Film Co., Ltd. (Minami-Ashigara, JP), September 3, 2002. 

K. Tasaka, T. Yajima, N. Kuzuhara, and H. Umeda. Optical compensation film, viewing angle compensation integral type polarizing plate and liquid crystal display apparatus. US Patent 7105213, assigned to Konica Minolta Holdings, INC (Tokyo, JP), September 12, 2006. 

Wang, Z., Folkenroth, J., Zhou, W., Zhang, Y., and Shi, X. (2012). Cellulose ether polymers as optical compensation fUms for LCDs-high birefringence and tunable optics, IDW/AD 12, Kyoto, Japan, pp. 499-502. 

In LCDs various LC modes of operation are applied like twisted nematic (TN) [5], super twisted nematic (STN)[6], vertically aligned nematic (VAN) [7,8], optically compensated birefringence (OCB) [9] and in plane switching (IPS) [10-12]. The LC mode used depends on the demands of a specific application, like the viewing angle, power consumption and manufacturing cost. 

Also, the chemistry and polymerization of discotic monomers has been reviewed [10]. Their current and emerging uses are in optical compensation films for liquid crystal displays, carbon nanostructures, organic electronics, solar cells, light-emitting diodes, and field-effect transistors. 

Iribarren I., Alemdn C., Regano C., Martinez de Ilarduya A., Bou J.J., Munoz-Guerra S., Stereocopolyamides derived from 2,3-di-O-methyl-D- and -L-tartaiic acids and hexamethylenediamine. 2. Influence of the configurational composition on the crystal structure of optically compensated systems. Macromolecules, 29, 1996, 8413-8424. 

FIGURE 3.5 (a) Natural orientation of a film of an No. (b) and (c) are controlled by the use of additives and surface treatment (above) along with a key to the molecular structure of the photopolymerizable No exploited in the Fuji optical compensation film. Examples of the types of materials used to control the orientation of the director at the air-liquid crystal and solid-liquid crystal interface (below). Reprinted with permission from Reference 14. Copyright 2002 Elsevier. 

SCHEME 3.3 Chemical structures of the revolutionary DLC compounds which have found real practical application in LCD devices as optical compensation films to enlarge the viewing angle and enhance the contrast ratio. 

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