Polymeric Shell Particles for Electrophoretic Displays
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Solution Overview
Problem
There is a demand for improved electrophoretic fluids and particles that can be easily dispersed in non-polar media, particularly for colored and white reflective displays, which require controlled size, reflectivity, density, and steric stability, and current methods are inefficient and require costly drying processes.
Innovation Solution
The development of particles comprising organic or inorganic pigment core particles encapsulated by a polymeric shell, using a process that includes polymerisable steric stabilisers, coupling reagents, and co-monomers, allowing for in-situ surface stabilisation and dispersion in non-polar solvents without the need for drying, enabling controlled particle properties and easy formulation of electrophoretic fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional methods are used to produce coloured and white reflective particles, then particle production is achieved, but the particles are difficult to disperse in non-polar media and require costly drying processes
Solution Approach 1:
The patent changes the surface chemistry parameters of the particles by incorporating polymerisable steric stabilisers that create a polymeric shell. This modifies the surface properties to be compatible with non-polar media, enabling direct dispersion without drying. The steric stabilisers alter the interfacial energy parameters between the inorganic core and organic medium.
Solution Approach 2:
The patent creates composite particles consisting of an inorganic pigment core encapsulated by an organic polymeric shell. This composite structure combines the reflective properties of inorganic materials with the dispersibility of organic polymers in non-polar media, eliminating the need for drying processes.
2Illumination intensity
If inorganic white reflective components are used, then reflectivity is improved, but dispersion in organic media becomes difficult
Solution Approach 1:
The patent applies local quality by creating a distinct polymeric shell layer around the inorganic core. The shell has different chemical properties (organic, polymer-based) than the core (inorganic pigment), providing local compatibility with non-polar media while preserving the core's reflective properties.
Solution Approach 2:
The polymeric shell acts as an intermediary between the inorganic pigment core and the organic dispersion medium. It mediates the interaction by providing a compatible interface that enables dispersion while allowing the core to maintain its reflective function.
3Manufacturing precision
If multiple process steps are used to incorporate pigment into particles, then particle properties can be controlled, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges multiple functions into a single polymerisation step. The coupling reagent simultaneously performs surface treatment of the inorganic core and provides anchoring points for polymer growth. The polymerisation process simultaneously creates the polymeric shell and incorporates steric stabilisers, achieving particle property control in one step rather than multiple sequential steps.
Solution Approach 2:
The coupling reagent performs preliminary surface treatment of the inorganic particles before polymerisation. This preliminary action creates reactive sites on the surface that enable subsequent polymer attachment, ensuring proper particle properties are established before the main polymerisation process begins.
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 approach results in particles with improved reflectivity, stability, and mobility, enabling efficient switching in electrophoretic displays with faster response times and reduced manufacturing costs, as well as the ability to produce monodisperse particles with tunable properties.
Implementation Method 1
a polymeric shell comprising monomer units of at least one polymerisable steric stabiliser
Implementation Method 2
facilitates covalent bonding of the polymeric coating to the titania during polymerisation
Implementation Method 3
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 comprising a core particle and a polymeric shell, a process for their preparation, electrophoretic fluids comprising such particles, and electrophoretic display devices comprising such fluids.