Photoalignment of Ferroelectric Liquid Crystals by Azodye Layers

Abstract

The photoinduced alignment of ferroelectric liquid crystals (FLCs) onto photochemically stable azo-dye films was studied. The alignment quality of FLC display cells depends mainly on the difference between the FLC surface energy and the aligning substrates surface energy; however, the structure and thickness of FLC layers are also important. The effect of the thickness of photoaligning azodye layer on the alignment quality and multiplex operation of passively addressed FLC display cells has been investigated. An optimal (about 3-5 nm) azo-dye layer thickness that provides both the highest multiplex operation steadiness and the best contrast ratio of the FLC display cells was found. The photoaligned FLC display cells showed the contrast ratio CR > 500 : 1 at the wavelength ¼ 0:63 mm both in surface stabilized and deformed helix FLC electrooptical modes.

Polarization-gratings approach to deformed-helix ferroelectric liquid crystals with subwavelength pitch

“…[27,28] for stratified anisotropic media. Mathematically, in this approach, the key formulas (37) and (38) give the transmission and reflection matrices of diffraction orders, T n and R n , expressed in terms of the linking matrix (33) which is related to the evolution operator (20) of the system of matrix equations (16) for the Floquet harmonics (14) derived from the Maxwell's equations for the lateral components of the electric and magnetic fields (10).…”

“…Following the method of Ref. [38], indium tin oxide (ITO) surfaces of FLC cells were covered with a 10-to-20-nm photoaligning substance, azobenzene sulfonic dye SD-1 layers. The azo-dye solution was spin coated onto an ITO electrode and dried at 155 • C.…”

“…Then computing the transmission and the reflection matrices (30) involve the following steps: (a) evaluation of the linking matrix (33); (b) calculation of the efficiency matrices (35) by solving the system of linear equation (34); (c) computing the matrices T n and R n from the formulas (37) and (38), respectively.…”

34.1: Deformed Helix Ferroelectric Display with Low Driving Voltage and Fast Response Time

“…In the short-pitch approximation, a DHF cell is shown to be optically equivalent to a uniformly anisotropic biaxial layer where one of the optical axes is normal to the bounding surfaces [8]. For in-plane anisotropy, orientation of the optical axes and birefringence are both determined by the voltage applied across the cell and represent the parameters that govern the transmittance of normally incident light passing through crossed polarizers.…”

P‐144: Electrooptic Response of FLC: Effect of Alignment Materials

“…Fast switching FLC display is a good candidate for the new generation of FSC-LCD, which is proved to be better in response time, than usually used nematic LC. One of the most crucial problems, which is usually faced in ferroelectric LCD such as quality of FLC alignment on sufficiently large surface area etc., can be effectively solved by a photo-alignment technology [4].…”