Multi-Chromophore Dyes for Improving Light Stability of Electro-Fluidic Displays

Electro-fluidic display (EFD) is a new reflective display based on electrowetting phenomenon which is applied to the outdoor billboard. Organic dyes are the most important materials for the color gamut and reliability of the EFD devices, which are always synthesized based on mono-chromophore dye in previous work. In this paper, we report our research on azopyrazolone as the chromophore to construct a polychromic macromolecular dye system. The light stability and photo-electric properties of these new dyes are researched detailed. It is found that the light stability of multi-chromophore dyes and backflow properties are much better than corresponding mono-chromophore dye.

Design of Switchable On/Off Subpixels for Primary Color Generation Based on Molybdenum Oxide Gratings

Structural color emerges from the interaction of light with structured matter when its dimension is comparable to the incident wavelength. The reflected color can be switched by controlling such interaction with materials whose properties can be changed through external stimuli such as electrical, optical, or thermal excitation. In this research, a molybdenum oxide (MoOx) reflective grating to get a switchable on/off subpixel is designed and analyzed. The design is based on subpixel on and off states that could be controlled through the oxidation degree of MoOx. A suitable combination of three of these subpixels, optimized to get a control of primary colors, red, green, and blue, can lead to a pixel which can cover a wide range of colors in the color space for reflective display applications.

Driving Waveform Optimization by Simulation and Numerical Analysis for Suppressing Oil-Splitting in Electrowetting Displays

Electrowetting display (EWD) is a new reflective display device with low power consumption and fast response speed. However, the maximum aperture ratio of EWDs is confined by oil-splitting. In order to suppress oil-splitting, a two-dimensional EWD model with a switch-on and a switch-off process was established in this paper. The process of oil-splitting was obtained by applying different voltage values in this model. Then, the relationship between the oil-splitting process and the waveforms with different slopes was analyzed. Based on this relationship, a driving waveform with a narrow falling ramp, low-voltage maintenance, and a rising ramp was proposed on the basis of square waveform. The proposed narrow falling ramp drove the oil to rupture on one side. The low-voltage maintenance stage drove the oil to shrink with a whole block. The proposed rising ramp was pushed the oil into a corner quickly. The experimental results showed that the oil splitting can be suppressed effectively by applying the proposed driving waveform. The aperture ratio of the proposed driving waveform was 2.9% higher than that of the square waveform with the same voltage.

All-Dielectric Metasurface with Ultrahigh Color Filtering and Polarization-Independent/Dependent Characteristics

All-dielectric nanostructure-based color filter (CF) has attracted huge interest in many fields due to its excellent optical properties. We present four metasurface-based CFs with different shapes on quartz substrates to generate pure blue, green and red colors. CFs show maximum reflection intensities of 99.6%, 99.7%, and 95.1% and the corresponding spectra bandwidths are 13 nm, 16 nm, and 14 nm for blue, green and red colors, respectively. The proposed metasurface-based CFs possess high color saturations and ultra-narrow bandwidths. In addition, metasurface-based CFs with different shapes show the tunability for color switching characteristics. These CFs designs will potentially benefit reflective display technologies, and their ultrahigh color filtering and polarization-independent/dependent characteristics are particularly useful for high resolution color printing, micro-LED, polarizer-switches, tunable color switches, and so on.

A Multi Waveform Adaptive Driving Scheme for Reducing Hysteresis Effect of Electrowetting Displays

Electrowetting display (EWD) is a new reflective display technology, which has the advantages of ultra-low power consumption, high contrast, fast response and full-color. However, due to a hysteresis effect, accurate gray scale display of EWDs cannot be achieved, which seriously restricted the display effect and performance of EWDs. In order to reduce the influence of hysteresis effect, a multi waveform adaptive driving scheme was proposed in this paper. Firstly, a multi waveform driving system was designed and implemented by a STM32 master chip and an AD5304 driver chip. The driving system could automatically select different driving waveforms according to the preset switching conditions. Then, different driving waveforms were designed and implemented according to different driving stages of EWDs. Finally, driving waveforms were mapped with each stage of the driving process one by one to realize the adaptive driving of multiple waveforms. The experimental results showed that, compared with the conventional square wave, the maximum hysteresis difference of hysteresis curve could be reduced by 39.19% with the multi waveform driving scheme.