Dynamic Adaptive Display System for Electrowetting Displays Based on Alternating Current and Direct Current

Abstract

As a representative of the new reflective display technology, electrowetting display (EWD) technology can be used as a video playback display device due to its fast response characteristics. Direct current (DC) driving brings excellent reflectivity, but static images cannot be displayed continually due to charge trapping, and it can cause afterimages when playing a dynamic video due to contact angle hysteresis. Alternating current (AC) driving brings a good dynamic video refresh ability to EWDs, but that can cause flickers. In this paper, a dynamic adaptive display model based on thin film transistor-electrowetting display (TFT-EWD) was proposed. According to the displayed image content, the TFT-EWD display driver was dynamically adjusted by AC and DC driving models. A DC hybrid driving model was suitable for static image display, which could effectively suppress oil backflow and achieve static image display while ensuring high reflectivity. A source data non-polarized model (SNPM) is an AC driving model which was suitable for dynamic video display and was proposed at the same time. Compared with DC driving, it could obtain smooth display performance with a loss of about 10 absorbance units (A.U.) of reflective luminance, which could solve the flicker problem. With the DC hybrid driving model, the ability to continuously display static images could be obtained with a loss of 2 (A.U.) of luminance. Under the AC driving in SNPM, the reflected luminance was as high as 67 A.U., which was 8 A.U. higher than the source data polarized model (SPM), and it was closer to the reflected luminance under DC driving.

Design of Multi-DC Overdriving Waveform of Electrowetting Displays for Gray Scale Consistency

“…When the pixel was in an “on” state, appropriate parameters had to be found to ensure that the pixel aperture ratio remained stable. When a constant voltage was applied, the electrowetting force decreased due to charge trapping [ 24 ]. It has been experimentally demonstrated that the trapped charge was released when the applied voltage was lowered [ 25 , 33 ].…”

“…An EWD changed pixels in the wettability of polar liquids in an insulating hydrophobic layer by applying a driving voltage between the upper and lower indium tin oxide (ITO) electrodes, resulting in change and displacement [ 24 ]. Each pixel of EWDs was principally comprised of a top plate, ITO/TFT glass, polar liquid, color oil, pixel wall, a hydrophobic insulating layer, and substrates.…”

A Driving Waveform with a Narrow Falling and High-Voltage Reset Structure for Improving the Stability of Electrowetting Displays

“…In order to test the suppression effect of the proposed driving waveform on oil film splitting, two different driving waveforms were selected for performance comparison, as shown in Figure 10A. The two driving waveforms being compared were the PWM driving waveform [25] and a driving waveform with a rising gradient [35]. In order to ensure consistency in the parameters, the high and low levels of the PWM driving waveform were set to 35 V and 0 V, respectively.…”

“…However, the response time of EWDs increased, and a high frame rate display could not be maintained. Then, an optimized driving waveform was proposed based on an overdriving voltage [25]. The overdriving voltage was introduced to shorten the response time in the oil film-splitting stage, and a DC driving voltage was applied to obtain the target luminance in the driving stage.…”

Editorial for the Special Issue on Advances in Optoelectronic Devices

“…So, trapped charges could be quickly released by the negative voltage. For the display system, a dynamic adaptive display system was proposed [ 17 ]. The driving model was dynamically adjusted according to the display contents.…”