Polymer dispersed nematic liquid crystal films with conical boundary conditions for electrically controllable polarizers

Abstract

Polymer dispersed nematic liquid crystal (PDNLC) films with conical boundary conditions at the LC-polymer interface are considered. The conical surface anchoring with tilt angle 40 • initiates forming the axial-bipolar director configuration inside nematic droplets. This droplet structure exhibits the strong scattering of light polarized parallel to the bipolar axis. In the initial state, the bipolar axes in all droplets are oriented randomly, and therefore PDNLC film scatters a light of any polarization. Electric field applied along the film plane orients the bipolar axes unidirectionally in the whole droplet ensemble, that results in its high polarization-dependent transmittance. Such PDNLC films can be used in the electrically controllable linear polarizers characterized by 89% value of the transmittance for the perpendicular polarized light and high extinction ratio 590:1 at the electric field 0.34 V/µm.

Nematic Structures under Conical Anchoring at Various Director Tilt Angles Specified by Polymethacrylate Compositions

“…This effect can be eliminated by adding 20% LC LN-396 into the polymer mixture. Such an amount of LN-396 is dissolved entirely, particularly, in polymer PiBMA [ 47 ], and LC droplets are not formed in PiBMA: PMMA film. In this case the structure with homogeneous azimuthal director orientation along the rubbing direction of PVA film is formed in all the samples ( Figure 4 ).…”

Polymer Dispersed Cholesteric Liquid Crystals with a Toroidal Director Configuration under an Electric Field

“…The application of an electric or magnetic field changes the orientation of the bipolar axis of the droplets in the case of tangential or conical boundary conditions [ 15 , 19 ] or switches the director structure from radial to axial in the case of homeotropic anchoring [ 20 ]. This leads to a change in light scattering [ 21 , 22 , 23 ] and absorption [ 24 , 25 ] of PDLC film, which can be used in optical shutters and smart films.…”

Recent Advances in The Polymer Dispersed Liquid Crystal Composite and Its Applications

“…Inside the LC droplet, the director configuration is mainly determined by boundary conditions (surface anchoring), LC material parameters and droplet shape and size. External factors (electric or magnetic fields, temperature, stress and so on) change the orientational structure which affects the light-scattering by LC droplets and, consequently, the light transmission of the PDLC film [23][24][25][26][27][28][29][30]. In addition, a slight difference in the refractive index (RI) of both the phases (LCs and polymer) has a significant effect on the light scattering properties of the PDLC films.…”