White Reflective Polymer Particles for Electrophoretic Displays
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Solution Overview
Problem
There is a demand for improved electrophoretic fluids with simple and cost-effective methods to produce white reflective particles that can be easily dispersed in non-polar media, suitable for low-power, low-cost, and lightweight display devices like electronic paper, which require long-term image retention without continuous voltage application.
Innovation Solution
A reverse emulsion solvent removal process is used to prepare white reflective polymer particles by forming a reverse emulsion with a polymer, white reflective particles, polar and non-polar solvents, and surfactants, followed by evaporative solvent removal, allowing for control of particle charge, size, and stability, resulting in particles with optimal scattering intensity and low density for use in electrophoretic displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional methods are used to prepare white reflective particles, then particle production is achieved, but dispersion in non-polar media is difficult and solvent contamination occurs
Solution Approach 1:
The invention changes the solvent system parameters by using a reverse emulsion approach where a polar solvent (water) is removed evaporatively from a non-polar continuous phase. This parameter change enables the particles to be formed directly in the non-polar media required for electrophoretic displays, eliminating solvent contamination and ensuring good dispersibility without requiring additional transfer steps.
Solution Approach 2:
The invention extracts the polar solvent (water) from the emulsion system through evaporative removal. By taking out the unwanted polar component, the particles are left dispersed only in the non-polar continuous phase, which is suitable for electrophoretic display applications and eliminates solvent incompatibility issues.
2Illumination intensity
If inorganic nanoparticles are used, then white reflective properties are achieved, but density is high and dispersibility in non-polar media is poor
Solution Approach 1:
The invention creates composite particles by combining inorganic white reflective nanoparticles (such as titania, alumina, or barium sulphate) with an organic polymer matrix. This composite structure maintains the high reflective properties of the inorganic core while the polymer coating reduces overall particle density and provides compatibility with non-polar dielectric media through appropriate surfactant selection.
Solution Approach 2:
The invention introduces an organic polymer and surfactant as intermediary materials between the inorganic nanoparticle core and the non-polar continuous phase. This intermediary layer improves dispersibility in non-polar media while maintaining the reflective properties of the inorganic core, and the polymer matrix helps reduce the effective density of the composite particles.
3Ease of operation
If electrophoretic fluids are formulated with conventional particles, then display function is achieved, but response time is slow and power consumption is high
Solution Approach 1:
The invention optimizes particle parameters including size (50-500 nm range), charge density, and surface properties to improve electrophoretic mobility. By controlling these parameters during the reverse emulsion process, the particles achieve faster response times and reduced power consumption while maintaining reliable display function.
4Manufacturing precision
If multiple processing steps are used to prepare particles, then particle properties are controlled, but manufacturing complexity increases and cost increases
Solution Approach 1:
The invention merges multiple functions into a single reverse emulsion process step. The process simultaneously achieves particle formation, solvent removal, and dispersion in the final non-polar media in one integrated operation, eliminating the need for separate processing steps and reducing manufacturing complexity while maintaining control over particle properties.
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
This process provides white reflective polymer particles with enhanced properties such as solvent resistance, non-swelling, high electrophoretic mobility, and faster response times, suitable for electrophoretic displays, while minimizing unwanted solvent contamination and enabling easy transfer to other solvents, thus addressing the need for improved electrophoretic fluids.
Implementation Method 1
forming a reverse emulsion comprising at least one polymer, at least one white reflective particle, at least one polar solvent, at least one non-polar solvent, and at least one surfactant
Implementation Method 2
removing the polar solvent or polar solvents by evaporative methods
Implementation Method 3
at least one surfactant
Data Source
AI summary
This invention relates to white reflective polymer particles prepared by a reverse emulsion solvent removal process, electrophoretic fluids comprising such particles, and electrophoretic display devices comprising such fluids.