Bookshelf orientation

The quasi-bookshelf orientations produced by AC-field treatment have been applied to passive matrix FLC displays. Rieger et al. reported that a quasi-bookshelf orientation induced by AC-field treatment showed a contrast ratio of 60 1 with a line-address time of 90 isec under the control of a 4-slot multiplexing addressing waveform with a bias of 4 1. They presented a 1.9" passive matrix FLC panel with 96 X 128 pixels that they had fabricated by using this method [8]. The specifications of their prototype FLC display are given in Table 6.1.2. T. Kitamura et al. also reported use of the AC-field treatment method to fabricate a passive matrix FLC display with 2000 x 2000 pixels [9]. The specifications of this display are summarized inThble 6.1.3. 

Extensive measurements of the Prederiks transition in various smectic C liquid crystals have been carried out by the Halle group [117, 118]. In experiments, the conventional sandwich cells with optically transparent electrodes were used. The director was oriented uniaxially by rubbing the electrodes and the smectic layers were tilted with respect to the cell plane (a bookshelf geometry). An electric field applied along the cell normal ( -direction), due to positive dielectric anisotropy, induces the director rotation around the normal to the smectic layers. Fig. 6.32. Two optical effects are observed ... 

The orientations of the molecules of the FLC materials are classified by the presence or absence of a helical structure. The most famous FLC device is the SSFLC (Surface Stabilized FLC) [1], in which the helical structure of the FLC material is unwound. While a variety of molecular orientations have been applied in SSFLC devices, three molecular orientations appear to be the most useful in practical FLC displays.These are the bookshelf-layered structure and the Cl-uniform (CIU) and the C2-uniform (C2U) orientations [2]. Each of these structures shows monostability or bistability, depending on the material and its alignment properties. The monostable orientations are applicable to active matrix FLC displays while the bistable orientations are applicable to passive matrix FLC displays. FLC displays with a helical orientation have also been investigated. One useful FLC mode with the helical orientation is the DHF (deformed-helix ferroelectric) mode [3]. This mode is monostable and is thus suitable for an active matrix drive method. 

Section 2 covers the DHF mode with a helical structure. The bookshelf structure, the Cl-uniform (CIU) orientation, and the C2-uniform (C2U) orientation are described in Sections 3, 4, and 5, respectively. Section 6 covers the stability of the molecular orientations in FLC devices exposed to shock. Weakness in this respect is one of the intrinsic problems of FLC displays. The layer rotation behaviour, an intrinsic behaviour of FLC displays, is described in Section 7. 

In a sense, the bookshelf layer structure (shown in Fig. 6.1.3) is the ideal molecular orientation for an SSFLC. One of the greatest merits of the bookshelf layer structure is its wide memory angle. The ideal memory angle in an SSFLC is 22.5° because the transmission of light of a wavelength A is given by the following equation. 

Fig. 6.1.3 Bookshelf and chevron layer structures, (a) Bookshelf layer structure, (b) Cl orientation of a chevron layer structure, (c) C2 orientation of a chevron layer structure.

Molecular orientation Quasi-bookshelf (AC field treatment method)... 

MoleculEm orientation Quasi-bookshelf (by using naphthalene compounds)... 

Mauzac et al. [28] oriented their networks at the isotropic to liquid crystalline phase transformation by applying an electric poling held [28]. However, the bookshelf alignment is not perfect. Finally Gebhard and Zentel [29] realized ultrathin free-standing ferroelectric Aims using a method of Skarp [30]. The prepolymer was spin-coated on an NaCl plate and photo-cross-... 

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