Electrophoretic Display Research Articles

Improving Electrophoretic Particle Motion Control in Electrophoretic Displays by Eliminating the Fringing Effect via Driving Waveform Design.

Electrophoretic display is realized by controlling colored nanoparticles moving in micrometer spaces via electrophoresis. The quality of information display is therefore affected by the unsynchronized particle moving speed and the mismatched electric signal according to the crosstalk of the electric field and inhomogeneous material distribution. In this work, we analyzed the mechanism of a fringe phenomenon that affected the information display quality of electrophoretic displays (EPDs). Electrical driving waveforms (voltage signals) are designed to reduce the fringe phenomenon. By using the optimizing driving waveform, we proposed that the fringe phenomenon is quantified as gray value that can be diminished by 25.5, while keeping a response time of 200 ms.

Driving Method of Three-Particle Electrophoretic Displays

The electrophoretic display (EPD) is the main solution to electronic papers, but most of them can display the image or text in black and white particles only. The users may prefer the EPD showing multiple colors rather than the black/white content only. In this paper, we introduce the driving system for a color EPD, which is composed of three kinds of particles. The system aims at optimizing the visual quality based on a new driving waveform by equipping with an optimization method for color and tone reproduction. The experimental result shows that the proposed EPD driving system can display three-color pictures with promising visual quality.

Quantitative Analysis of Color Differences within High Contrast, Low Power Reversible Electrophoretic Displays

Quantitative color analysis is performed on videos of high contrast, low power reversible electrophoretic deposition (EPD)-based displays operated under different applied voltages. This analysis is coded in an open-source software, relies on a color differentiation metric, ΔE* 00, derived from digital video, and provides an intuitive relationship between the operating conditions of the devices and their performance. Time-dependent ΔE* 00 color analysis reveals color relaxation behavior, recoverability for different voltage sequences, and operating conditions that can lead to optimal performance.

Uniform Insulating Properties of Low-Temperature Curable Gate Dielectric for Organic Thin-Film Transistor Arrays on Plastic Substrate

Achieving a high-resolution display on a plastic substrate requires a low-temperature process to ensure dimensional stability during fabrication process, including the deposition of gate dielectrics. Evaluation platform to confirm the uniform insulating properties of organic dielectric material prior to actual application to organic thin-film transistor arrays were proposed. This test method enabled verification of the suitability of the low-temperature curable dielectric and chemical resistance during the fabrication process. A cross-linked poly(hydroxy imide) that can be cured at a low temperature of 130°C exhibited stable insulating properties in a large area that sudden breakdown was not observed in an electric field up to 4 MV/cm. Thiophene-thiazole-based copolymer semiconductor was used as an active layer and inkjet-printed. In all the processes, the temperature of the substrate was kept below 130 °C, and 4.8-inch electrophoretic display panels on a polyethylene naphthalate substrate with a resolution of 98 dpi was demonstrated.

Fast-response and monodisperse silica nanoparticles modified with ionic liquid towards electrophoretic displays

The facile synthesis of electrophoretic particles for electrophoretic displays (EPDs) with fast response and precise image control is a challenge. In this work, monodisperse silica nanoparticles were prepared by a sol-gel process in reverse microemulsion combined with solvent-thermal treatment, and modified with ionic liquid. The silica nanoparticles before and after surface modification are all monodisperse and smooth spheres. They also own suitable densities and excellent chromaticity for EPDs. The structure of ionic liquid modifiers shows remarkably influence on surface property and electrophoretic property of modified silica nanoparticles. The modified silica nanoparticles show improved hydrophobicity favoring for dispersion stability and suspension stability in the dispersant. The surface charge performance of modified silica nanoparticles are depending on competitive cooperation between ion pairs and alkyl groups of ionic liquids, and can be adjusted through tuning ionic liquid structure. The fabricated EPD prototypes show response time of 180–191 ms in the electrophoretic display cell with 0.2 mm thickness, much faster than the commercial EPDs.

Improvement of video playback performance of electrophoretic displays by optimized waveforms with shortened refresh time

Electrophoretic display (EPD) has become one of the most important display technologies due to its bistability, low power consumption and outdoor readability. In this work, an image processing algorithm, which aims to enable video playback on EPD device without image distortion and grayscale loss by reducing the particle moving distance in EPD, is proposed and verified. The refresh time could be shortened by 22.2% with a video playback speed of more than 10 frames per second (fps) being achieved. This method could reduce the EPD switching time for quicker information displaying, and potentially extend the applications of EPD with video-like display property in the future.

38‐3: Full‐Color Flexible Electrophoretic E‐Paper with Interfacial Engineering and Transferring Process

A full color microcapsule‐type of electrophoretic display (EPD) with facile transferring method was firstly demonstrated. Using this method, we spatially deployed the different color microcapsules into subpixels. The %NTSC reaches 19.1%, which is the highest record among all the microcapsule‐type of EPD display reported.

An adaptive generation method for electrophoretic display driving waveform design

AbstractElectrophoretic display (EPD) technology is attractive when used for reading devices such as e‐paper because of its paper‐like appearance. EPD driving is more complex than other display technologies such as liquid crystal display or organic light emission diode because the driving result of a pixel strongly depends on the initial display state. The particle size and distribution in the EPD film may vary, even if the initial state is the same. Therefore, the display devices vary between different manufacturing batches. Furthermore, different display modes such as videos, pictures or documents need different driving waveforms to achieve an optimal result. EPD manufacturers need to build a customized driving waveform for every manufacturing batch. This is very inconvenient if new applications on EPD are to be developed. And the workload is huge. In this work, an adaptive method is described for automatically creating EPD driving waveforms to fit different conditions. The central idea of this method is generally adjusting the driving time and the voltage state after getting the feedback from a measurement model. In this method, a new driving waveform is used to reduce refresh time and visual flicker. The experimental results show that the proposed approach can automatically and adaptively generate an EPD driving waveform with reasonable quality.

Synthesis of charged hybrid particles via dispersion polymerization in nonpolar media for color electrophoretic display application

ABSTRACTDirect synthesis of charged hybrid particles in non‐polar media has not been widely described in the literature but can lead to many applications such as electrophoretic displays. In this work, we propose a way to synthesize charged hybrid particles within the electrophoretic medium (Toluene or Isopar G) in the presence or not of additives (Charge Control Agent, CCA). The particles synthesis was performed by Nitroxide‐mediated Radical Polymerization (NMRP) via dispersion polymerization in aliphatic hydrocarbon solvents leading to stable chargeable particles with a good size control. Hybrid particles are successfully charged by reaction with functional monomers or addition of CCA to obtain electrophoretic particles. The performance of a dual‐color red/white ink in a display was demonstrated with a test‐cell. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 338–348

An Analysis of Reflectivity and Response Time by Charge-to-Mass of Charged Particles in an Electrophoretic Display

A reflective electronic display that uses negatively and positively charged particles has excellent bistability, a welldefined threshold voltage, and an extremely fast response time in comparison with other reflective displays. This type of display shows images through the movement of charged particles whose motion depends on the value of q/m (charge per mass for a particle). However, the ratio q/m can easily be changed by the forces acting on the charged particles in a cell of the panel and by friction that occurs after mixing oppositely charged particles and in the particle-insertion process. In this study, we propose a method to determine the appropriate range of q/m by using the reflectivity and response time of charged particles to modify q/m. In this manner, the electrical and optical properties of reflective displays are improved.

Encapsulation of modified pigment yellow 110 (PY110) for electrophoretic display

Abstract

Fabrication of compact poly(methyl methacrylate-co-butyl methacrylate-co-acrylic acid) microcapsules for electrophoretic displays by using emulsion droplets as templates

Microcapsules with smooth, transparent, and compact walls used for electrophoretic displays (EPDs) were prepared and characterized. The approach to fabricate EPD microcapsules was based on templating an oil-in-water emulsion stabilized by monodispersed poly(methyl methacrylate-co-butyl methacrylate-co-acrylic acid) latex particles synthesized by dispersion polymerization. The individual latex particles were then transformed into robust capsule walls by successively using solvent swelling, covalent cross-linking, and sintering. The diameter of the emulsion droplets was controlled by changing the concentration of latex in the emulsion, and the thickness of the wall changed according to the diameter of the latex particles. These microcapsules for EPDs were applied successfully in preparing a clock display panel controlled by a single-chip microprocessor operated at a low direct current voltage, demonstrating that these microcapsules can be used in EPDs.

Preparation of environment friendly gelatin–arabic gum microcapsules in Isopar M system for electrophoretic display

A series of functional microcapsules for electrophoretic display (EPD) prepared by complex coacervation technology utilising gelatin and arabic gum as a wall material are presented. The authors have investigated the Isopar M electrophoretic fluid containing blue-white, red-white and yellow-white particles modified by the physical coating as core materials of microcapsules, respectively. The mass ratio of wall/core material is a key factor influencing the yield of microcapsules. The surface of microcapsule was characterised by optical microscopy and scanning electron microscopy. The display prototypes based on the red-white, blue-white and yellow-white microencapsulated electrophoretic fluids have been prepared. The contrast ratios of prototypes were found to be 1.62, 1.67 and 1.22, respectively.

Preparation of electrophoretic nanoparticles for electronic paper

C.I. Pigment Red 48 : 2 (P.R.48 : 2) and C.I. Pigment Red 57 : 1 (P.R.57 : 1) composite particles encapsulated with three kinds of polyethylene (PE), which had different molecular chain structure, were prepared by dispersion polymerisation method. The modified pigments were characterised by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), UV–Vis spectroscopy and chroma. The modified particles were dispersed in Isopar L : C2Cl4 = 1 : 1 and then successfully incorporated in an electrophoretic display cell, and P.R.48 : 2/high-density polyethylene (HDPE) particles, which had electron-withdrawing groups and coating materials with high crystallinity and without short-chain branches, had the best properties and their highest contrast ratio on the same device was found to be 2.67, which was better than those of pigments modified with others PE.

57-2:Invited Paper: Flexible Electrophoretic Displays with Novel Drive Schemes for Wearables and Mobiles

Displays for Watches and Wearables must fill most of the device front, which requires small IC and interconnect areas. This isn't usually possible with amorphous silicon TFTs, but we have applied new driving methods and processes to minimize edges and make flexible electrophoretic displays suitable for Watches, Wearables and Mobiles.

Preparation and Characterization of Microcapsule-Encapsulated Colored Electrophoretic Fluid in Trifluorotoluene System for Electrophoretic Display

Trifluorotoluene was used as a liquid suspending fluid for electrophoretic display (EPD). The dispersion stability, chargeability, and response time of electrophoretic particles suspended in trifluorotoluene were investigated. Hyperdispersant and assistant hyperdispersant (CH-11B) could provide satisfactory dispersion stability in trifluorotoluene electrophoretic fluid. The contrast ratio of simple electrophoretic display devices reached 2.95, 3.93, and 1.41, respectively, and the response time was 305 ms/348 ms, 512 ms/415 ms, and 140 ms/371 ms, respectively. All of the devices remained stable within 30 min after outage. The coating process using the method of screen printing was studied with trifluorotoluene microcapsules as coating materials. The counts of mesh and coating layer were key factors influencing the performance of coating. Microcapsule type EPD prototypes showed outstanding display results without coating defects.

High-resolution inkjet-printed organic thin film transistor array with commercially applicable source-drain electrode process

High-resolution inkjet printing of an organic thin film transistor (OTFT) array for mass-production is still regarded as an immature technology due to the difficulty in controlling the dimension of pattern and registry with other layers in commercial large-scale substrates. Especially, in the case of on organic gate insulator (OGI) in an inkjet-printed OTFT array, it is impossible to use plasma pre-treatment of the OGI for the hydrophobicity required for high-resolution inkjet printing of an organic semiconductor (OSC) due to its non-selectivity between organic layers, both inside and outside the channel area. A novel and commercially applicable process of the source-drain (SD) electrode prior to inkjet printing of the OSC in the bottom contact structure not only allowed a selective plasma treatment for high-resolution inkjet printing of OSC on OGI without the extra photolithographic process, but also protected the channel interface from the harmful outcomes of wet or plasma processes. This method enabled uniform electrical characteristics of more than 300 thousand pixels of an OTFT array for a backplane. Based on these results, a 5.7 inch electrophoretic display (EPD), with a high resolution of 140 dots per inch (DPI), on a plastic substrate was successfully demonstrated.

Preparation and application of black hollow carbon-doped titania composite spheres for electrophoretic displays

In this paper, hollow carbon-doped titania composite spheres were prepared through a template-assisted method. The hollow spheres were obtained via deposition of inorganic shell on the surface of polymer latex template with Ti(OBu)4 as precursor and then freeze-drying process was used to reduce breaking and fragments during calcinations. After calcinations in Ar atmosphere, carbon layer was coated onto the surface of hollow microspheres by adsorption to the resulting hollow black spheres with various crystalline structures at different calcination temperatures. The hollow spheres were characterized with scanning electron microscopy (SEM), transmission electron microscopy, energy dispersive X-ray spectrometer, thermo gravimetric analysis, Brunauer–Emmett–Teller, X-ray diffraction, ultraviolet and visible absorption and electrophoresis apparatus. The results showed that the hollow TiO2/C spheres were monodisperse and average diameters were 220 nm approximately. Furthermore, the new kind of composite material was applied to electrophoretic display as black particles. The electrophoretic mobility and zeta value in Isopar-G were −2.60e−006 cm2 V−1 s−1 and −35.31 mV respectively, which illustrated its potential application prospect in development of electrophoretic ink.

Electrophoretic Ink Display Prepared by Jelly Fig Pectin/Gelatin Microspheres

A brand new Bio-Electronic ink (Bio-E ink) display device was prepared and characterized in this study. Semiconductor material, copper phthalocyanine (CuPc) was modified by cationic surfactants, cetylpyridinium chloride (CPC), as the core material, and the shell of capsule was prepared by jelly fig pectin, gelatin and sodium dodecyl sulphate (SDS). Here, jelly fig pectin was provided as the shell material for the first time. Chemical structure of the modified CuPc was characterized by Fourier Transform Infrared Spectrometer (FTIR). The core-shell microcapsules were achieved by coacervation method in an oil/water (O/W) emulsion system. The particle size and morphology of microcapsules were affected by the concentrations of SDS and pH values of the O/W emulsion system. A new microcapsule-based electrophoretic display device was presented. Its image display ability of the microcapsules electrophoretic device was presented as appropriated electric power was applied, and the response time was 0.06 sec under 0.1 V/mm of electric field. Moreover, we found that its image contrast ratio of display device was influenced by the particle sizes of the microcapsules.

Preparation of chromatic composite hollow nanoparticles containing mixed metal oxides for full-color electrophoretic displays

The green and blue hollow nanospheres were prepared via emulsifier-free emulsion polymerization and the Pechini sol–gel process. They exhibit bright color and hollow structures with uniform size and shape, which also present excellent performance and quick response of electrophoretic display.