Frequency Modulation and Capacitance-Amplification of TN-LCD Embedded with Metal Nanoparticles of Pd and Ag Using Equivalent Circuit Analysis

Abstract

A twisted nematic (TN) liquid crystal displays (LCDs) with embedded Pd and Ag nanoparticles covered with a diffusion cloud exhibits peculiar frequency-dependent behavior. In particular, no TN response is observed below the frequency, f₂ (\(\sim\)2 Hz) that is far below the dielectric relaxation frequency, f_R, whereas above this frequency, revival of the TN response occurs, where LC of 5CB was used. This device is called frequency modulation (FM) TN-LCD and its behavior is attributed to the reduction of the dielectric anisotropy \(\Delta\varepsilon\) far below the relaxation frequency, f_R. However, above this frequency, the revival of the torque driving the TN-CD occurs, and the operation of the TN-LCD is revived with a quick response speed. The reduction of \(\Delta\varepsilon\) may be due to the prevailing of the amplified dielectric constant caused by the inclusions covering the entire region. However, above f_R, this amplification gradually vanishes and the normal TN-operation is revived due to the revival of the 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, A_c, is equal to10 and 52 with the NPs of Pd and Ag, respectively, through a postulation of negative \(\varepsilon\)₂ for the inclusions (NPs and diffusion cloud) is also presented.