Composite Electrophoretic Particles for Stable Color Displays
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Solution Overview
Problem
Existing electrophoretic displays face issues with long-term image quality due to particle settling, particularly in gas-based media, and the challenge of using small particle organic pigments that are not suitable for light scattering applications.
Innovation Solution
Development of composite electrophoretic particles with a light-scattering inorganic core, such as titania, coated with a light-transmissive colored organic pigment shell, allowing for the creation of electrophoretic media that can utilize small particle organic pigments effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If small particle organic pigments are used directly in electrophoretic media, then color gamut and optical density are improved, but particles settle rapidly due to insufficient light scattering and low viscosity of the medium
Solution Approach 1:
The patent creates composite particles by coating light-scattering inorganic pigment particles (such as titanium dioxide) with light-transmissive organic pigment shells. This composite structure combines the light scattering properties of inorganic particles with the color properties of organic pigments, preventing settling while maintaining optical density and color gamut.
Solution Approach 2:
The invention applies different materials to different parts of the particle structure: the core uses light-scattering inorganic pigment for stability and light scattering, while the shell uses light-transmissive organic pigment for color. This local differentiation allows each component to perform its optimal function.
2Reliability
If inorganic pigments are used for light scattering, then particle stability is improved, but color gamut is limited compared to organic pigments
Solution Approach 1:
The patent combines light-scattering inorganic pigment cores with light-transmissive organic pigment shells to create composite particles that exhibit both the stability and light scattering of inorganic particles and the broad color gamut of organic pigments.
Solution Approach 2:
The composite particle structure serves multiple functions simultaneously: the inorganic core provides light scattering and structural stability, while the organic shell provides broad color absorption and transmission properties, achieving multi-functionality in a single particle system.
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 composite particles provide high optical density and a wider range of colors, improving the long-term image quality and color gamut of electrophoretic displays while preventing particle settling, thus enhancing the stability and performance of electrophoretic media.
Implementation Method 1
a light-scattering inorganic core
Implementation Method 2
a light-transmissive colored shell of an organic pigment
Implementation Method 3
a plurality of charged particles move through a fluid under the influence of an electric field
Data Source
AI summary
A particle for use in an electrophoretic display comprises a light-scattering inorganic core and a light-transmissive colored shell of an organic pigment. The core may be titania and the shell may be formed of particles having an average particle size less than 700 nm. The particles are produced by treating a light-scattering inorganic pigment with a polymer which adsorbs on both the inorganic pigment and an organic pigment; and adding the organic pigment and allowing the organic pigment to mix with the polymer-coated inorganic pigment. The particles may have a polymer coating.