Electro-Optical Effects of a Color Polymer-Dispersed Liquid Crystal Device by Micro-Encapsulation with a Pigment-Doped Shell

Chao Chen,Dae Kim,Chul Jhun

doi:10.3390/cryst9070364

Chao Chen, Dae Kim + Show 1 more

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https://doi.org/10.3390/cryst9070364

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Journal: Crystals	Publication Date: Jul 17, 2019
Citations: 14	License type: CC BY 4.0

Affiliation: Hoseo University, Shanghai Jiao Tong University

Abstract

Polymer-dispersed liquid crystals (PDLCs) refer to nematic liquid crystals, which are embedded in a polymer matrix. A conventional PDLC device is fabricated by phase separation. However, this method leads to non-uniform electro-optical characteristics of the device due to the non-uniform size distribution of the liquid crystal droplets. Moreover, the PDLC device is switched between the transparent state and the scattering state so that a full color scheme is intrinsically impossible without a color filter. In this paper, a fabrication method for a color PDLC device with uniform size and shape for liquid crystal droplets is proposed. Droplets of a fairly uniform size in large quantities can be obtained by means of membrane emulsification. Microcapsules are fabricated by complex coacervation with gelatin and gum arabic. By adding red, green, and blue pigments, color microcapsules are obtained. The electro-optical effects of the fabricated color PDLC devices are also demonstrated. The driving voltage of the device is 90 V, and the switching time is 8.3 ms. In the turn-on state, the measured hazes of red, green, and blue PDLC devices are 16.89%, 15.82%, and 18.55%, respectively, while in the turn-off state, the measured hazes of those devices are 65.21%, 67.32%, and 70.76%, respectively.

Highlights

Polymer-dispersed liquid crystals (PDLCs) refer to nematic liquid crystals, which are embedded in a polymer matrix [1]
Unlike conventional liquid crystal devices [2,3,4,5], which rely on birefringence, a PDLC device exploits the light scattering effects
To address both athecore–shell non-uniform size distribution andsize the full color display, The we propose a color color PDLCs with structure of uniform is investigated

Summary

Introduction

Polymer-dispersed liquid crystals (PDLCs) refer to nematic liquid crystals, which are embedded in a polymer matrix [1]. Unlike conventional liquid crystal devices [2,3,4,5], which rely on birefringence, a PDLC device exploits the light scattering effects. The typical PDLC device can switch between a transparent state and a light scattering state by the electric field. It has been used in a variety of optical devices such as switchable windows [6], shutters [7], gratings [8], etc. PDLCs can be operated without a polarizer, reducing the loss of light. Fergason [9] proposed a micro-encapsulation method to form liquid crystal droplets within the polymer, and later West [10]

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