The Strength of Rubbing Worked on Polyimide Films for Aligning Nematic and Chiral Smectic Liquid Crystals: Controlling Pretilt Angles and Some Electrooptic Performances of LCDs

Abstract

The degree of work done on polyimide films in the rubbing process with a nylon fabric was detected and evaluated in terms of induced birefringence. Strong and weak rubbing (effecting two extremes) gave rise to the optical retardation of 1 degree and 0.1 degree, respectively, with a resolution of 0.1 degree. Generation of a pretilt angle of up to 10 degrees (even up to 30 degrees) for nematic liquid crystals was achieved by performing weak rubbing in a specially synthesized polyimide which was successfully used to fabricate supertwisted nematic liquid crystal displays. Fairly good bistability in a ferroelectric liquid crystal device was obtained by weak rubbing.

Cooperative liquid-crystal alignment generated by overlaid topography

“…Current LC devices such as displays require specific and predictable LC alignment characteristics [1][2][3][4][5] and future LC applications, such as in organic photovoltaics (OPV), will depend on effective alignment of novel materials systems [6]. In the latter case, for example the discotic and polymeric composite systems under development can be difficult to orient in electrically efficient geometries, a problem complicated by the nanoheterogeneity required for efficient PV performance.…”

Investigation of Refractive Indices of Free-Standing Films by Ellipsometry

“…The stainless steel plates also act as electrodes to apply an electric field ($ 9.0 V=mm) parallel to the smectic layer of FSF. The phase difference D of the outgoing light between the p-polarized and s-polarized light, was measured by means of transmission ellipsometry system which is composed of photoelastic modulator, He-Ne laser and a pair of Glan-Thompson prisms [3]. The phase difference D and the angle of amplitude ratio W of the reflected light was measured by the variable angle spectroscopic ellipsometry (VASE, J.…”

Surface induced liquid-crystal alignment studied by optical second-harmonic generation

“…Assuming the interaction between molecules to be negligible, the xc') tensor can be related to the hyperpolarizability tensor ac2) of the adsorbed molecules by: # = N,(G $&a$. (2) Here N, is the surface density of molecules and (G $$) denotes an appropriate average over molecular orientations of the transformation matrix from the molecular coordinate axes ($,,;i,t> to the laboratory system (z$).…”