Composite Particles with Cross-linked Polyurea for Electrophoretic Displays
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Solution Overview
Problem
Existing electrophoretic displays face challenges with long-term image quality due to particle settling, which affects their service life and widespread adoption, despite offering good brightness, contrast, and low power consumption.
Innovation Solution
The development of composite particles with a cross-linked polyurea network that incorporates small pigment or dye particles, allowing for efficient electrokinetic mobility and stability, formed through a process involving water-dispersible polyfunctional isocyanates and a water-miscible solvent, creating particles suitable for use in electrophoretic media.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If particles are used in electrophoretic displays to achieve good brightness and contrast, then display quality is improved, but particles tend to settle over time which reduces service life
Solution Approach 1:
The patent applies composite materials by combining a base particle with a cross-linked polyurea network and hydrophilic oligomeric groups to create a composite particle structure. This composite structure maintains the optical properties needed for brightness while adding functional groups that prevent settling, thus resolving the contradiction between display quality and service life.
Solution Approach 2:
The patent changes the chemical and physical parameters of the particle by introducing a cross-linked polyurea network with specific hydrophilic oligomeric groups. This parameter change modifies the particle's interaction with the electrophoretic medium, preventing settling while maintaining the optical properties required for good brightness and contrast.
2Speed
If particles are made smaller to improve electrokinetic mobility, then switching speed is improved, but particle stability decreases leading to settling
Solution Approach 1:
The composite particle structure combines a base particle with a cross-linked polyurea network that provides stability. This allows small particle sizes for high electrokinetic mobility while the cross-linked network and hydrophilic groups maintain stability and prevent settling, resolving the contradiction between speed and stability.
Solution Approach 2:
The patent applies local quality by creating a specific cross-linked polyurea network structure with hydrophilic oligomeric groups at specific locations on the particle. This localized structural modification provides the necessary stability without affecting the overall small size of the particle, enabling both high mobility and stability.
3Stability of the object's composition
If a cross-linked polyurea network is formed throughout the base particle to enhance stability, then particle stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating the cross-linked polyurea network formation into the particle synthesis process itself, rather than as a separate post-processing step. The cross-linking occurs during emulsion formation and agitation, integrating the stability-enhancing structure into the base manufacturing flow and reducing overall complexity.
Solution Approach 2:
The cross-linked polyurea network forms through self-service by utilizing the chemical reactivity of water-dispersible polyfunctional isocyanates that automatically cross-link during the emulsion process. The system self-organizes into the cross-linked structure without requiring additional complex manufacturing steps, achieving stability enhancement through the inherent chemistry of the materials used.
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 enhance the stability and mobility of electrophoretic media, improving the long-term image quality and service life of electrophoretic displays by preventing particle settling and ensuring efficient electrokinetic switching.
Implementation Method 1
providing either a solution containing a dye or a dispersion containing a pigment in a water-dispersible polyfunctional isocyanate dissolved in a water-miscible solvent, forming an emulsion of the solution/dispersion in water, agitating the emulsion while the polyfunctional isocyanate is converted into a cross-linked polyurea
Implementation Method 2
forming an emulsion of the solution/dispersion in water, agitating the emulsion while the polyfunctional isocyanate is converted into a cross-linked polyurea
Implementation Method 3
charged particles move through a fluid under the influence of an electric field
Data Source
AI summary
A composite particle is provided that comprises a base particle comprising at least a pigment or dye and cross-linked polyurea, a plurality of hydrophilic oligomeric groups, and a plurality of amine groups on the exterior portion of the base particle, and a steric stabilization polymer which is chemically bonded or physi-sorbed on the surface of the base particle. The cross-linked polyurea may form a network throughout the base particle. A method of making the composite particle includes providing either a solution containing a dye or a dispersion containing a pigment in a water-dispersible polyfunctional isocyanate dissolved in a water-miscible solvent, forming an emulsion of the solution/dispersion in water, agitating the emulsion while the polyfunctional isocyanate is converted into a cross-linked polyurea, and separating the composite particle containing the cross-linked polyurea and the dye/pigment from the emulsion.