Eight sample panels using an indium tin oxide(ITO)-coated glass substrate were fabricated, with barrier ribs formed of 55 ${mu}m$ height and 10 ${mu}m$ width. The upper and lower substrates were designed with the same panel condition, so a cell gap of 110 ${mu}m$ was obtained. The charged particles in a cell consisted of $TiO_2$ (for white color) or carbon black (black color), negative or positive charge control agents, and a polymer. The average diameter of the two types of particles was commonly 10 ${mu}m$, and their q/m value was -4.5 ${mu}C/g$ and +4.5 ${mu}C/g$, respectively. The electrically opposite particles mixed by an agitator were loaded into their cells by a simple particle-loading method. The discharging process proceeded at a humidity of 80% and a temperature of $30^{circ}C$. Reflectivity was measured depending on discharging time, and a hysteresis curve by bias voltage obtained for comparison between the neutralized and non-neutralized panel, in which the superior optical property of the neutralized panel was ascertained.