Research on Suitable Viscosity and Driving Waveform of Chromatic Electrowetting with Good Photoelectric Characteristics

This paper proposes a kind of periodic complex ramp pulse driving waveform in the electrowetting display system with suitable viscosity ink. Firstly, considering the fluid-motion characteristics of different viscosity inks, the relationship between the contact angle and viscosity of inks in the liquid-oil-solid three-phase contact display system is calculated to obtain the suitable viscosity range and driving voltage range. Secondly, the physical model of ink motion with different viscosity is established by COMSOL simulation. Then, During the ink shrinkage movement after applying voltage, the change of the meniscus height at the oil-liquid interface is calculated. Finally, the appropriate viscosity range of the ink movement is verified and obtained based on the meniscus height. On this basis, after applying the driving voltage of different amplitude and frequency respectively, the ink movement situation is observed to design a suitable driving waveform. The results show that when the viscosity of ink fluid is between 0.005 and 0.015Pa·s, the higher the voltage amplitude and the lower the frequency, the higher the meniscus height of ink shrinkage, which is consistent with the characteristics of magenta ink tested in the experiment. Experimental tests show that the driving waveform designed in this paper can not only suppress the phenomenon of oil film splitting, backflow and contact angle saturation hysteresis, but also improve the ink response speed and pixel aperture ratio, in which the aperture ratio is increased to 68.69%. This research is of great significance to optimize the structure of fluid material and the design of driving in electrowetting display.