Modes normally white/black

To obtain a comparable viewing angle with VA and IPS, OCB requires more sophisticated optical compensation based on a discotic material [58]. Figure 8.31 shows the compensation schemes for a normally white OCB mode. The fundamental idea is similar to that for TN. The retardation matching between the cell and the optical compensation film is especially important for the OCB mode, partially because the black state of the normally white OCB cell has a finite residual retardation value that must be compensated by an optical film. For example, any retardation fluctuation of the cell or the film is easily noticeable. The OCB system requires a high level of uniformity. And the cell parameters, as well as the film parameters, should be optimized in order to maximize the optical performance. 

The intensities J(A) in the on- and off-states are averaged with the function of the sensitivity of the human eye t/(A) and the energy distribution of the illumination source H X) over the visible spectrum (380-780 nm). The electrooptic effect in the twist cell placed between parallel and crossed po-laroids is called, in [98], the normally black and normally white mode, in accordance with the appearance of the twist cell in the off state. Contrast ratios in the white mode are considerably higher than in the black mode, as the luminance in the on state for a normally white mode could be very small and limited only by the quality of polaroids and orientation. 

In the case that the transmissive axes of the upper and lower polarizers are placed parallel, the OFF state of the display is black and this configuration is called normally black mode. Since the normally black mode gives some light leakage in the black state, the normally white mode is adopted in aTFT-LCD. 

Contrast Ratio of the Normally Black and Normally White Mode... 

Figure 4 DynDom [67] analysis of the first two normal modes of human lysozyme. Dark grey and white indicate the two dynamic domains, separated by the black hinge bending region. The vertical line represents a hinge axis that produces a closure motion in the first normal mode. The horizontal line represents a hinge axis that produces a twisting motion in the second normal mode. (Adapted from Ref. 68.) The DynDom program is available from the Internet at http //md. chem.rug.nl/ steve/dyndom.html.

Figure 7. Steicoprojeclions of the 514, 490, 398, and 388-cm normal modes of showing the equilibrium (white circles and black bonds) and vibrationally displaced molecules (shaded circles and white bonds). Beneath each mode is a schematic representation of the predominant pattern of motion and the linear combination of achiral cyclohexanone motions that generate the vibration. (Reproduced with permission from ref. 77. Copyright 1984 American Chemical Society.)...

To visualize the normal modes, we use the notation of Nalewajski [8] the modes are represented by diagrams showing the relative changes in the electron populations black and white circles correspond to an electron outflow (U.,e < 0)... 

In order for LCDs to expand into future applications, the major challenge is to increase contrast. This subsection provides an overview of directions for further contrast improvements. Moving picture quality performance improvement is shown in Fig. 1.22 for liquid crystal materials for VA mode. The contrast is defined as the ratio of black-and-white brightness. IPS, FFS, and VA modes are normally black, ... 

The liquid crystal is oriented vertically when no voltage is applied and tilts under an electric field. With a pair of polarizers whose absorption direction is perpendicular to each other (referred to as crossed Nicols), a so-called normally black display is realized, in which the display is black when no voltage is applied and white with an applied voltage (Fig. 6.6). This mode has been reported in 1971, at around the same time as the twisted nematic (TN) mode [46]. 

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