Colored Polymer Particles for Full-Color Electrophoretic Displays
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Solution Overview
Problem
Current electrophoretic displays (EPDs) lack a bright full-color system and require complex cell structures and drive schemes, with existing colored particles being difficult to disperse in non-polar media and prone to color leaching.
Innovation Solution
Development of specifically engineered polymer particles through a one-step reaction process using polymerizable dyes, which are covalently bonded to monomers, allowing for excellent control over particle size, charge, and color, and are dispersible in non-polar media without color leaching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional colored particles are used in EPDs, then color display is achieved, but the particles are difficult to disperse in non-polar media and prone to color leaching
Solution Approach 1:
The patent uses composite particles consisting of a hydrophobic polymer core (polystyrene or polymethyl methacrylate) that provides color stability and resistance to leaching, combined with a hydrophilic polymer shell (polyacrylic acid or polyacrylamide) that enables dispersibility in non-polar media through steric stabilization and electrostatic repulsion. This core-shell composite structure resolves the contradiction between color stability and dispersibility.
Solution Approach 2:
The patent modifies the surface properties of the particles by controlling the molecular weight and composition of the hydrophilic shell polymer, and by adjusting the surface charge density through pH control or ionic surfactant addition. These parameter changes enable the particles to maintain both color stability and dispersibility in the required media.
2Adaptability or versatility
If different coloured particles are used in a single pixel, then full color display is achieved, but complex cell structures and drive schemes are required
Solution Approach 1:
The patent segments the color display function by using differently colored particles (cyan, magenta, yellow, or RGB particles) dispersed in a single electrophoretic medium, where each particle type carries a specific color. By controlling the electrophoretic movement and accumulation of these segmented color particles at the electrode interface, full-color display is achieved without requiring separate cells for each color, thus simplifying the overall cell structure.
Solution Approach 2:
The patent creates a universal electrophoretic display system where a single cell structure can display multiple colors by utilizing particles with different colors but similar electrophoretic properties. The same electrode configuration and driving scheme can manipulate cyan, magenta, yellow, or RGB particles to produce various colors, giving the system multi-functional color display capability without increasing structural complexity.
3Adaptability or versatility
If existing coloured particles are used, then color display is possible, but they require complicated preparation processes
Solution Approach 1:
The patent incorporates the coloring function into the particle preparation process itself by adding water-soluble dyes or pigments during the emulsion polymerization stage. This preliminary action of coloring the particles during synthesis eliminates the need for subsequent separate coloring steps, simplifying the overall preparation process while maintaining color display capability.
Solution Approach 2:
The patent merges multiple functions into a single preparation process: particle synthesis, surface modification for dispersibility, and coloration are all accomplished in one emulsion polymerization step. By combining these previously separate operations into a unified process, the patent simplifies manufacturing while producing particles with all required properties for color display.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process enables the production of high-quality, monodisperse colored polymer particles suitable for full-color EPDs with improved electrophoretic mobility, optical clarity, and cost-effective production, maintaining color stability over time.
Implementation Method 1
the reaction of at least one polymerisable dye, at least one monomer, at least one initiator
Implementation Method 2
the reaction of at least one polymerisable dye, at least one monomer, at least one initiator
Implementation Method 3
charged particles move to the electrode of opposite polarity
Data Source
AI summary
This invention relates to colored polymer particles preferably with surface functionality for charge retention, a process for their preparation, the use of these particles for the preparation of an electrophoretic device, color electrophoretic displays comprising such particle, and new water-soluble dyes.