P‐137: Measurement of the LC Pretilt Angle and Polar Anchoring in Cells with Homogeneous and Inhomogeneous LC Director Configuration and Weak Anchoring on Organosilicon Aligning Films

Abstract

New optical and electro-optical methods of LC director average tilt angle measurement are described in LC cells with homogeneous and inhomogeneous LC director distribution. The LC pretilt on both LC substrates can have the same or opposite direction. Both LC pretilt angle and polar anchoring energy values have been measured for both polar and weak polar liquid crystal materials on aligning films of organosilicon compounds (OC) of different molecular structure. The method developed can be used also in optical compensator design.

Measurement of the liquid crystal pretilt angle in cells with homogeneous and inhomogeneous liquid crystal director configuration

“…The W value is in the range from 10 −5 to 10 −4 J m −2 . For some OC coatings, the W value is comparable with the LC polar anchoring on the polyimide aligning layers [9,28].…”

“…The pretilt angle values are in the range from 0°to 90°versus the OC molecular structure [27,28]. The θ values intermediate between 0°and 90°are formed owing to the interaction of three processes that take place when the cell is filled in and the LC flows into the cell: LC alignment in the Couette or Poiseuille flow [6,29], surface interaction between the LC and OC film, and LC Franck elasticity.…”

“…aligning films of OC compounds [17,28,34]. Nematic LCs with both positive and negative dielectric anisotropy have been used.…”

P‐123: Oblique Light Incidence onto Hybrid Aligned Nematic (HAN) Cells for Optical Compensators

“…A phase difference parameter Φ=ΔФ/ΔФ max was introduced in [16,17]. The phase retardation difference ΔΦ is reduced to its maximum value ΔФ max =2πΔnL/λ, Δn=n e -n o is the LC birefringence.…”

“…The calculation method was firstly described in [16][17][18] for the LC cells with homogeneous, splay or bend director configuration. On the base of such calculation a method of the LC pretilt angle measurement has been developed in [18] for the cells with unknown arbitrary LC director configuration.…”