Abstract
A twisted nematic (TN) liquid crystal display (LCD) with embedded Ag nanoparticles (NPs) covered with a diffusion cloud exhibits peculiar frequency dependent behavior. In particular, no TN response is observed below the dielectric relaxation frequency, fR, whereas above this frequency, revival of the TN response occurs. Such a device is called a frequency modulation (FM) TN-LCD, and its behavior is attributed to the reduction of the dielectric anisotropy Δɛ far below the relaxation frequency, fR. However, above this frequency, the revival of the torque driving the TN-LCD occurs, and the TN-LCD operation is revived with a fast response speed. The reduction of Δɛ may be due to the prevalence of the amplified dielectric constant caused by the inclusions covering the entire region. However, above fR, this amplification gradually vanishes, and the normal TN-operation is revived due to the revival of dielectric torque force. In this paper, an interpretation of the FM-LCD operation through dielectric spectroscopy and equivalent circuit analysis is presented. Interpretation of the dielectric constant amplification [whose factor, AC, is equal to 52 through a postulation of negative ɛ2 for the inclusions (NPs and diffusion cloud)] is also presented.
Highlights
In a previous paper, the authors investigated the frequency modulation (FM) twisted nematic-liquid crystal display (TN-LCD) and TB, which is called ECB-LCD devices with embedded metal nanoparticles (NPs) of Pd.1,2 Both TN and TB LCDs exhibited frequency-dependent operation
No LCD operation occurs in the low frequency region below the dielectric relaxation frequency, f R, whereas above this frequency, revival of the TN response occurs with a fast response speed
The mechanism of the FM-TN operation with respect to the frequency dispersion of dielectric anisotropy obtained from a sample cell with a (NLC) 5CB AgNP-TN LCD is discussed
Summary
The authors investigated the frequency modulation (FM) twisted nematic-liquid crystal display (TN-LCD) and TB (tunable birefringence), which is called ECB (electrically controlled birefringence)-LCD devices with embedded metal nanoparticles (NPs) of Pd. Both TN and TB LCDs exhibited frequency-dependent operation. The authors investigated the frequency modulation (FM) twisted nematic-liquid crystal display (TN-LCD) and TB (tunable birefringence), which is called ECB (electrically controlled birefringence)-LCD devices with embedded metal nanoparticles (NPs) of Pd.. The authors investigated the frequency modulation (FM) twisted nematic-liquid crystal display (TN-LCD) and TB (tunable birefringence), which is called ECB (electrically controlled birefringence)-LCD devices with embedded metal nanoparticles (NPs) of Pd.1,2 Both TN and TB LCDs exhibited frequency-dependent operation. At high frequency, this amplification gradually vanishes, and the revival of the torque driving the TN-LCD occurs, enabling the revival of the TN normal operation This behavior is common for similar LCDs such as 5CB-TN-Pd NPs and ECB-NPs.. An equation for the short relaxation time of the inclusion is derived and compared with that of the host medium
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