Microcapsule Classification via Electrostatic Mobility
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Solution Overview
Problem
Conventional methods for producing microcapsules for electrophoretic display devices result in a broad particle size distribution, leading to high coefficients of variation and physical damage during classification, making it difficult to achieve precise classification on an industrial scale, especially for soft microcapsules.
Innovation Solution
A particle classification apparatus with a connecting flow passage, conical part, and barrel part is used to classify microcapsules in an aqueous medium, generating a circulating flow that allows for precise separation without physical damage, achieving a coefficient of variation in particle diameter not higher than 14%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional classification methods (sieve or slit) are used to classify microcapsules, then particle size distribution can be controlled, but soft microcapsules suffer physical damage and deformation
Solution Approach 1:
The patent replaces mechanical classification systems (sieves and slits that cause physical contact and damage) with an electrostatic classification system. Microcapsules are charged and separated based on their electrophoretic mobility in an electric field, allowing precise particle size distribution control without mechanical stress or physical damage to the microcapsule structure.
Solution Approach 2:
The patent changes the classification parameter from physical dimension (mechanical filtering) to electrical property (electrophoretic mobility). By applying an electric field and utilizing the charged nature of microcapsules, classification is achieved based on electrical parameters rather than mechanical constraints, preserving microcapsule integrity while achieving precise size sorting.
2Manufacturing precision
If classification treatment is performed on soft microcapsules using conventional methods, then particle size can be controlled, but the microcapsules become deformed and slip through classification structures
Solution Approach 1:
The patent replaces mechanical classification structures (sieves and slits that cause deformation and slipping) with an electrostatic field-based classification system. Soft microcapsules are classified based on their electrophoretic mobility in response to an applied electric field, eliminating mechanical contact that causes deformation and slipping, thereby achieving reliable and precise classification.
Solution Approach 2:
The patent introduces an electric field as an intermediary medium for classification. Instead of direct mechanical interaction between microcapsules and classification structures, the electric field acts as a mediator that exerts forces on charged microcapsules based on their size and charge characteristics, enabling precise classification without physical deformation.
3Manufacturing precision
If conventional classification methods are used, then some particle size control is achieved, but the process is complex and not suitable for industrial scale production
Solution Approach 1:
The patent replaces complex mechanical classification processes (multiple sieves, slits, and manual operations) with a streamlined electrostatic classification system. The electrostatic method requires only an electric field application and charge injection, significantly reducing device complexity and enabling easy scaling to industrial production while maintaining precise particle size distribution control.
Solution Approach 2:
The patent creates a universal classification system based on electrophoresis that can handle various microcapsule types (hard and soft) and size ranges with a single apparatus design. This multi-functional approach eliminates the need for multiple specialized mechanical classification devices, reducing overall system complexity and facilitating industrial scale production.
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 enables the production of microcapsules with a small coefficient of variation in particle diameter, enhancing display performance by reducing defective microcapsules and improving reflectance and contrast in electrophoretic display devices, suitable for both hard and soft microcapsules.
Implementation Method 1
particles are classified from the dispersion contained in the dispersion reservoir by generating a circulating flow of the dispersion in the barrel part until the dispersion reaches the discharging flow passage from the connecting flow passage
Implementation Method 2
a particle classification apparatus having a connecting flow passage toward a dispersion reservoir, a conical part, a barrel part, and a discharging flow passage, in this order from a bottom side of the apparatus
Data Source
AI summary
There is disclosed a process for producing microcapsules for electrophoretic display devices, including classifying microcapsules for electrophoretic display devices from a dispersion containing microcapsules in an aqueous medium, using a specific particle classification apparatus of the particle settling type. The resultant microcapsules for electrophoretic display devices are used, as their applications, for sheets for electrophoretic display devices, electrophoretic display devices, and electronic equipments.