Bookshelf structures

Unfortunately, the ideal bookshelf structure is difficult to make. Usually the electrodes are covered by polymer layers and rubbed unidirectionally. This provides a good alignment of the director along the electrodes and the bookshelf ... 

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. 

While the bookshelf layer structure has strong merits for display applications, it is not easy to obtain the bookshelf structure due to the intrinsic temperature dependence of the tilt angles of FLC materials. Three major approaches to obtaining a bookshelf layer structure have been investigated. 

The stripe-shaped texture parallel to the rubbing direction is observed due to the formation of periodic undulation of the layer structure (Fig. 6.3.19). In the case that a strong AC voltage is applied, the chevron structure is deformed into the bookshelf structure and the strain occurs. The strain is relaxed by the rotation of the layer direction [55] which forms the periodic layer undulation. 

In Fig. 6.3.19, the structure of the stripe-shaped texture is shown. The width of the stripe becomes equal to the cell gap and the layer rotation angle becomes equal to chevron angle [68]. In certain conditions the tilted bookshelf structure can also be realized in this the width of the stripe becomes twice that of the cell gap [54]. 

Monostable SSFLC mode with tilted bookshelf structure... 

On a macroscopic scale, the spontaneous polarization vector in the optically active phase spirals about an axis perpendicular to the smectic layers (Fig. 20), and sums to zero. This macroscopic cancellation of the polarization vectors can be avoided if the helical structure is unwound by surface forces, by an applied field, or by pitch compensation with an oppositely handed dopant. The surface stabilized ferroelectric liquid crystal display utilizes this structure and uses coupling between the electric field and the spontaneous polarization of the smectic C phase. The device uses a smectic C liquid crystal material in the so-called bookshelf structure shown in Fig. 21a. This device structure was fabricated by shearing thin (about 2 i,m) layers of liquid crystal in the... 

Figure 73. The simple bookshelf structure with essentially zero pretilt would lead to ideal optical conditions for materials with 2 0 equal to 45°. In reality the smectic layers adopt a much less favorable chevron structure. This decreases the effective switching angle and leads to memorized P states that are not in the direction of the field (a, b). A convenient multiplexing waveform scheme together with a properly chosen value of the material s bi-axiality 9e may enhance the field-on contrast relative to the memorized (surface-stabilized) value (c), by utilizing the dielectric torque from the pulses continuously applied on the columns (after [142, 143]).

A homogeneous planar surface alignment is imposed by shearing the sample (or by appropriate alignment layers), whereby the smectic layers develop perpendicular to the two confining glass plates, forming the so-called bookshelf structure. 

Nito, K., H. Takanashi, and A. Yasuda. 1995. Dynamics of FLCs with a tilted bookshelf structure using time-resolved FTIR spectroscopy. Liq. Cryst. 19 (5) 653-658. 

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