Black Polymer Particles for Stable Electrophoretic Displays
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Solution Overview
Problem
Existing electrophoretic displays face challenges with black particles that are difficult to disperse in non-polar media, suffer from settling issues, and leach dye, leading to charging problems and photo/oxidation degradation.
Innovation Solution
Development of polymer particles comprising monomer units with polymerisable dyes, charged co-monomers, and crosslinking co-monomers, which are easily dispersed and do not leach dye, allowing for controlled particle size and high dye loading, reducing unreacted dye and oligomers, and enhancing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If carbon black is used for black particles, then availability and cost are improved, but dye leaching and charging issues occur
Solution Approach 1:
The patent uses composite polymer particles comprising both carbon black and colored polymer components. This composite structure allows the particles to maintain the availability and cost benefits of carbon black while the polymer matrix prevents dye leaching and charging issues by providing a stable, non-absorbing structure that retains electrophoretic charge.
Solution Approach 2:
The patent changes the physical and chemical parameters of black particles by synthesizing them as polymer particles with controlled size (0.1-2.0 µm), specific density (1.03-1.07 g/cm³), and compositional parameters (carbon black content 5-50 wt%). These parameter changes eliminate the harmful effects of conventional carbon black while maintaining its availability.
2Stability of the object's composition
If copper chromite is used for black particles, then color stability is improved, but density increases causing settling issues
Solution Approach 1:
The patent changes the density parameter of black particles from the high density of copper chromite to a controlled range of 1.03-1.07 g/cm³ for polymer particles. This parameter change maintains color stability through the polymer matrix while eliminating settling issues by reducing density and matching it closely to the dispersion medium density of 1.00-1.05 g/cm³.
3Illumination intensity
If polymer particles with high dye loading are used, then color depth is improved, but dye leaching increases
Solution Approach 1:
The patent uses a polymer matrix structure that acts as a flexible shell encapsulating the dye molecules. This polymer shell (composed of monomer units from polymerisable dye, monomer, and crosslinking co-monomer) provides a stable environment that maintains high color depth through high dye loading while preventing dye leaching into the dispersion medium.
Solution Approach 2:
The patent creates composite polymer particles where the polymer matrix (composite of polymerisable dye, monomer, and crosslinking co-monomer) provides both the color depth through high dye loading and prevents leaching through the stable polymer structure that does not absorb gases and liquids like conventional carbon black.
4Device complexity
If conventional black particles are used, then simplicity is maintained, but electrophoretic mobility is poor
Solution Approach 1:
The patent changes the surface charge parameter and size parameter of particles to optimize electrophoretic mobility. Polymer particles are engineered with controlled size (0.1-2.0 µm) and surface charge through the polymer matrix composition, enabling fast electrophoretic response while maintaining relatively simple particle structure without complex coatings or multi-layer structures.
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 solution provides stable, high-loading black polymer particles that maintain color fastness, reduce settling, and prevent dye leaching, enabling efficient and cost-effective production of electrophoretic displays with improved performance.
Implementation Method 1
polymer particles for use in electrophoretic devices comprising monomer units of a) at least one polymerisable dye, b) at least one monomer... by a process for the preparation of such polymer particles... These polymerisable dyes are incorporated throughout the particles and not just at the shell giving a greater loading of dye into the particle
Implementation Method 2
An EPD generally comprises charged electrophoretic particles dispersed between two substrates, each comprising one or more electrodes. If a voltage is applied between the electrodes, charged particles move to the electrode of opposite polarity
Data Source
AI summary
This invention relates to polymer particles, a process for their preparation, the use of these particles for the preparation of an electrophoretic device, electrophoretic displays comprising such particle, and new polymerisable dyes.