Porous Polymeric Shell Particles for Electrophoretic Displays
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Solution Overview
Problem
There is a demand for improved electrophoretic fluids and a simple method to produce coloured and white reflective particles that can be easily dispersed in non-polar media, with existing methods requiring complex processes and expensive drying steps.
Innovation Solution
The development of particles comprising organic or inorganic pigment core particles encapsulated by a micro-, meso-, or macro-porous polymeric shell, using a process that involves polymerisation with a porogen to create particles with controlled size, reflectivity, and steric stability, allowing for easy dispersion in non-polar media without the need for drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If particles are produced using existing methods, then coloured and white reflective particles can be obtained, but the process requires complex steps and expensive drying steps
Solution Approach 1:
The patent combines multiple production steps into a single one-pot polymerisation process. The porous polymeric shell is formed simultaneously with particle formation in the presence of porogen, eliminating the need for separate drying steps and reducing overall process complexity while maintaining particle quality
Solution Approach 2:
The patent extracts the drying step from the production process entirely. By forming porous shells in situ during polymerisation using porogen, the method eliminates the need for subsequent drying operations, simplifying the process and reducing equipment requirements
2Stability of the object's composition
If particles are produced with high density, then particle stability is improved, but reflectivity decreases
Solution Approach 1:
The patent incorporates porogen during polymerisation to create porous polymeric shells surrounding the pigment particles. These porous structures reduce the overall particle density compared to solid shells, improving reflectivity by creating refractive index differences, while the polymeric matrix maintains sufficient structural stability
Solution Approach 2:
The patent creates composite particles with a core-shell structure where the porous polymeric shell combines low-density polymeric material with pigment cores. This composite structure optimizes the balance between stability and reflectivity by leveraging the properties of both components
3Stability of the object's composition
If particles are dispersed in aqueous media, then particle stability is improved, but solvent contamination and disposal issues occur
Solution Approach 1:
The patent changes the dispersion medium from aqueous to organic solvents. The porous polymeric shells are designed to be compatible with organic media, providing adequate particle stability in non-aqueous environments and eliminating water-related contamination and disposal issues
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 method enables the production of particles with controllable size, reflectivity, and density, providing excellent reflectivity and electrophoretic mobility, and can be used in electrophoretic displays without the need for expensive drying steps or solvent recycling.
Implementation Method 1
The pores also have low refractive index which can improve the overall reflectivity of a particle by creating regions of low to high refractive index change
Implementation Method 2
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 particles for electrophoretic displays, a process for their preparation, electrophoretic fluids comprising such particles, and electrophoretic display devices comprising such fluids.