Abstract
The electro-optical features of the PDLC films applied with a low-frequency square wave voltage were investigated. The transmittance curves indicated the double frequency of the applied voltage at 0–50 Hz, which resulted from the relaxation of an internal electric field polarized by ions in LC droplets. When the local electric field was reversed, the internal polarization electric field could be maintained and superimposed on the local electric field. The relaxation of the internal polarized electric field resulted in the relaxation of the transmittance. Furthermore, the transmittance curves changed with the frequency of the applied voltage.
Highlights
Polymer-dispersed liquid crystal (PDLC) is a composite material consisting of LC droplets randomly dispersed into an isotropic polymer matrix and represents a significant new class of electro-optical materials [1,2,3,4]
For LC with positive dielectric anisotropy, LC droplets can be in the direction of the applied electric field so that PDLC films can be switched from an opaque off-state to a highly transparent on-state [7,8]
Eint was investigated by observing the electro-optical response of a PDLC film to direct current (DC) and low-frequency sinusoidal wave-driving voltages [23]
Summary
Polymer-dispersed liquid crystal (PDLC) is a composite material consisting of LC droplets randomly dispersed into an isotropic polymer matrix and represents a significant new class of electro-optical materials [1,2,3,4]. The free ions could decrease the dielectric constant and refractive index in LC droplets [16] and induce an internal polarization electric field (Eint ) to affect the hysteresis and memory state in the PDLC films [8,17,18]. Eint was investigated by observing the electro-optical response of a PDLC film to direct current (DC) and low-frequency sinusoidal wave-driving voltages [23]. We investigated the evolving curve of transmittance with time (T-t) with a square-wave voltage of 0–50 Hz. depending on the characteristics of the T-t curves in different frequency ranges, the dynamic behavior and the electro-optical effect based on Eint were investigated. It was revealed that Eint can increase Eeff when the polarity of the AC square wave voltage is reversed
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