Interpretation of frequency modulation TN-LCD embedded with metal nanoparticles using equivalent circuit analysis

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.