Light transmission of polymer-dispersed liquid crystal layer composed of droplets with inhomogeneous surface anchoring

2016 ◽  
Vol 120 (1) ◽  
pp. 143-152 ◽  
Author(s):  
V. A. Loiko ◽  
V. Ya. Zyryanov ◽  
A. V. Konkolovich ◽  
A. A. Miskevich
Keyword(s):  
Liquid Crystal ◽  
Light Transmission ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Inhomogeneous Surface ◽  
Surface Anchoring ◽  
Polymer Dispersed Liquid Crystal ◽  
Polymer Dispersed

Surface-Induced Flexoelectric Domains in Asymmetrically Strong-Weak Anchored MBBA Films

1982 ◽  
Vol 37 (4) ◽  
pp. 334-341
Author(s):  
H. P. Hinov
Keyword(s):  
Liquid Crystal ◽  
Electric Field ◽  
Dielectric Anisotropy ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Surface Anchoring ◽  
Threshold Voltages ◽  
Domain Period ◽  
Cell Thickness

Abstract The longitudinal surface-induced flexoelectric domains, previously obtained in symmetrically weak-anchored nematic layers have been further investigated in asymmetrically strong-weak anchored MBBA layers. The threshold voltages indicating the onset of the flexoelectric instabilities are high for thin cells (d = 9 μm, Uth = 10 V) and small for thick cells (d = 150 μm, Uth =1.5 V). Pronounced minima in the curves p vs. d and Uth vs. d, where p is the domain period and d is the cell thickness, were obtained. The flexoelectric domains were replaced by electrohydrodynamic instabilities only in the case of strong azimuthal anchoring of the liquid crystal layer.The role of the sign and the value of the dielectric anisotropy, the homogeneity of the electric field as well as the asymmetry in the surface anchoring are discussed in detail.

Surface Anchoring and Electro-Optics in Polymer-Dispersed Liquid-Crystal Films

1996 ◽  
Vol 425 ◽  
Author(s):  
Karl Amundson ◽  
Mohan Srinivasarao
Keyword(s):  
Liquid Crystal ◽  
Film Formation ◽  
Field Pattern ◽  
Director Field ◽  
Surface Anchoring ◽  
Liquid Crystal Films ◽  
Polymer Dispersed Liquid Crystal ◽  
Crystal Films ◽  
Polymer Dispersed ◽  
Micrometer Scale

AbstractPolymer-dispersed liquid crystal (PDLC) films are composed of micrometer-scale droplets of liquid crystal (typically nematic) in a polymeric matrix. They can be switched with an electric field from a scattering to a transparent state, and are of interest for use in flat-panel displays. The electro-optics of PDLC films, and the director field pattern within the nematic droplets, are strongly influenced by the surface anchoring condition at the liquid crystal - polymer matrix interface. To understand the role of surface anchoring, we studied the electro-optics of photopolymerized PDLC films composed of a liquid crystal and acrylates as a function of temperature. Properties depend strongly upon the choice of the acrylate. With several acrylate matrix materials, the nernatic director field undergoes a reversible, temperature-driven configurational transition, accompanied by dramatic changes in electro-optical properties. We find that the surface anchoring behavior is very sensitive to the polymer structure as well as several parameters of PDLC film formation. Several surface anchoring transitions are used in a study that shows strong evidence for surface memory in PDLC films.

The Effects of Film Thickness, Light Polarization, and Light Intensity on the Light Transmission Characteristics of Thermochromic Liquid Crystals

2006 ◽  
Vol 129 (3) ◽  
pp. 372-378 ◽  
Author(s):  
Timothy B. Roth ◽  
Ann M. Anderson
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Light Intensity ◽  
Temperature Measurement ◽  
Light Transmission ◽  
Transmission Spectra ◽  
Crystal Layer ◽  
Liquid Crystal Layer ◽  
Thermochromic Liquid Crystal ◽  
Thermochromic Liquid Crystals

Thermochromic liquid crystal materials change their crystalline structure and optical properties with temperature, making them useful in temperature measurement applications. This paper presents the results of a study to develop a temperature measurement system that uses light transmission through thermochromic liquid crystals instead of light reflection. We painted Hallcrest R25C10W sprayable liquid crystals on a clear surface and placed it in a spectrophotometer. The amount of light transmitted at monochromatic wavelengths from 400nm to 700nm was measured for temperatures from 25°C to 55°C under conditions of nonpolarized, linearly polarized, and cross-polarized light, for three light intensity levels, and three liquid crystal layer thicknesses. As the temperature was increased the amount of light transmitted through the liquid crystal layer increased. When the liquid crystals are in their active range the transmission spectra exhibit an s-curve shape and the percent of light transmitted through the liquid crystals at a fixed temperature increases with increasing wavelength. We detected significant changes in the transmission spectra for temperatures from 27°C to 48°C, whereas when used with reflected light the thermochromic liquid crystals are useful over a significantly smaller range. As the thickness of the thermochromic liquid crystal layer increases or as the incoming light intensity decreases, the amount of light transmitted through the liquid crystals decreases. We also investigated the effects of temperature overheat on the transmission spectra and found that heating the thermochromic liquid crystals above their active range increases the amount of light transmission. However, when the liquid crystals are cooled below their active range they return to their original state. We have analyzed the spectrophotometer data in a number of ways including: (a) total amount of light transmitted, (b) amount of red, green, and blue light transmitted; and (c) spectral curve shape characteristics (peak transmission, inflection wavelength and wavelength for peak transmission) all as a function of temperature. A linear relationship exists between temperature and all of these variables which we believe can be exploited for the development of a charge coupled light camera based light transmission system for temperature measurement.

scholarly journals Polymer Dispersed Cholesteric Liquid Crystals With a Toroidal Director Configuration under an Electric Field

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 732
Author(s):  
Anna P. Gardymova ◽  
Mikhail N. Krakhalev ◽  
Victor Ya. Zyryanov ◽  
Alexandra A. Gruzdenko ◽  
Andrey A. Alekseev ◽  
...  
Keyword(s):  
Optical Properties ◽  
Liquid Crystal ◽  
Electric Field ◽  
Point Defects ◽  
Structural Response ◽  
Optical Filters ◽  
Response Curves ◽  
Polymer Dispersed Liquid Crystal ◽  
Dichroic Dye ◽  
Polymer Dispersed

The electro-optical properties of polymer dispersed liquid crystal (PDLC) films are highly dependent on the features of the contained liquid crystal (LC) droplets. Cholesteric LC droplets with homeotropic boundaries can form several topologically different orientational structures, including ones with single and more point defects, layer-like, and axisymmetric twisted toroidal structures. These structures are very sensitive to an applied electric field. In this work, we have demonstrated experimentally and by computer simulations that twisted toroidal droplets reveal strong structural response to the electric field. In turn, this leads to vivid changes in the optical texture in crossed polarizers. The response of droplets of different sizes were found to be equivalent in terms of dimensionless parameters. In addition, the explanation of this phenomenon showed a comparison of theoretical and experimental structural response curves aids to determine the shape of the droplet. Finally, we demonstrated that the addition of a dichroic dye allows such films to be used as optical filters with adjustable color even without polarizers.

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