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We have presented the brightness changes in positive and negative dielectric anisotropy liquid crystal (P-LC and N-LC) Author Keywordsoxide semiconductor; In-Ga-Zn-O; eye strain; fringe field switching; flexoelectric effect; low power consumption; low frequency driving IntroductionLiquid crystals (LCs) have been widely studied in many fields [1,2] and applied to liquid crystal displays (LCDs) [3] successfully at present. Twisted nematic (TN), vertical alignment (VA), in-plane switching (IPS) and fringe-field switching (FFS) [4] are mainly the well-known driving modes in LCDs from small-size panel to TV application. In recent years, FFS with wide viewing angle and high LC efficiency characteristic has been widely used to high resolution smart-phone, tablet, notebook, monitor etc. In order to reduce the power consumption and extend the using time for mobile device, some works [5][6][7] have shown the low power methods based on the indium gallium zinc oxide (IGZO) thin-film transistor (TFT), where the extremely low leakage current is the key feature to enable a still image to be held for a long period. That is to say, the interval between data altering time can become more longer than that of conventional 60Hz panel. Then we will acquire the benefit of low power by reducing the data frequencies. Nevertheless, human eyes can perceive the brightness difference (BD) at the time of data rewriting. Therefore several methods [8,9] have implemented to eliminate the flicker so-called the eye-strain. One focuses on improving the dielectric constants of a LC and resistivities of an alignment layer, the other provides more than one VCOM driving scheme to suppress the eye-strain. However, they don't study the enhanced FEE under low-frequency driving in FFS mode that has been reported recently [10].In this paper, we propose a method to analyze the eye-strain by measuring the brightness changes using a photo-detector system under low-frequency driving. According to the analysis, we find that the cause of the eye-strain should result from BHRE and FEE.It is also noted that FEE is the critical factor to affect the eye-strain in P-LC. Hence, in order to eliminate the eye-strain, both BHRE and FEE must effectively be decreased when developing the low power technology by reducing the frame rate. ExperimentWe prepare a ~8.0 inch high-definition LCD based on amorphous-IGZO TFT to observe the eye-strain under low-frequency operation. The parameters of the LC panel are listed in Table 1. Here we use the Si-biased detector connecting with oscilloscope system (Tektronix TDS-3034B) to measure the brightness changes at the frequency of 1Hz. A schematic of the experimental instrument is shown in Fig. 1. All experiments were performed at room temperature. The width of the pixel electrode, the distance between pixel electrode and cell gap are 2.2 m, 3.8 um and 3.4 m, respectively.

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