Electrophoretic Particle Surface Modification for Low Dielectric Solvents
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Solution Overview
Problem
Electrophoretic display media face challenges in achieving high threshold voltage and reducing display defects such as reduced display density and mixed color display, especially when using solvents with low dielectric constants, which affect the charging and migration of electrophoretic particles.
Innovation Solution
The use of electrophoretic particles with a core material composed of a resin, a nitrogen-containing heterocyclic compound, and a coloring agent, along with a covering layer formed from a resin with both dispersion medium-philic and -phobic parts, enhances the charge quantity and threshold voltage, allowing for independent migration of particles and multicolor display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If solvents with low dielectric constants are used in electrophoretic display media, then the display device can achieve lower power consumption and faster response, but the charging and migration of electrophoretic particles is adversely affected, leading to reduced display density and mixed color display
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrophoretic particle surface by introducing specific functional groups (carboxyl, hydroxyl, amino groups) and controlling surface chemistry. This changes the interaction between particles and low dielectric constant solvents, enabling effective charging and migration even in non-aqueous environments, thus resolving the contradiction between using low dielectric constant solvents for energy efficiency and maintaining display density reliability
Solution Approach 2:
The patent creates composite electrophoretic particles with a core-shell structure where the surface is modified with specific functional groups and potentially coated with materials that enhance charge retention. This composite structure allows the particle to function effectively in low dielectric constant solvents by combining the core material properties with surface functional groups that facilitate proper charging behavior, thereby maintaining display density while using energy-efficient solvents
2Quantity of substance
If the surface of electrophoretic particles is modified to increase charge quantity, then threshold voltage increases and particle migration is enhanced, but display defects such as reduced display density and mixed color display may occur
Solution Approach 1:
The patent applies local quality modification by introducing specific functional groups (carboxyl, hydroxyl, amino) at the surface of electrophoretic particles rather than uniformly throughout the entire particle. This localized surface modification increases charge quantity where needed while maintaining the core particle properties, thus enhancing threshold voltage and migration without causing display defects
Solution Approach 2:
The patent carefully controls the concentration and type of surface functional groups to optimize charge quantity. By adjusting the density and distribution of these functional groups on the particle surface, the patent achieves the desired threshold voltage and migration characteristics while avoiding over-charging that would lead to display defects such as mixed color display
3Power
If electrophoretic particles are designed for high threshold voltage, then particle migration and multicolor display are improved, but the ratio of reversed polarity particles increases causing display defects
Solution Approach 1:
The patent modifies the surface chemistry parameters of electrophoretic particles by introducing specific functional groups that control charge polarity. This changes the electrical properties of the particles to achieve high threshold voltage while minimizing reversed polarity, thus improving both migration performance and display uniformity
Solution Approach 2:
The patent applies localized surface treatment with specific functional groups that enhance threshold voltage without creating reversed polarity regions. This localized modification ensures uniform charge distribution across the particle surface, preventing display defects while achieving the desired high threshold voltage for effective migration and multicolor display
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 configuration increases the threshold voltage and reduces the ratio of reversed polarity particles, thereby improving display quality by minimizing display defects like reduced density and mixed color issues, even in solvents with low dielectric constants.
Implementation Method 1
electrophoretic particles in a liquid and alternately moving the electrophoretic particles to the visual field and the rear field in the cell by the application of electric field
Implementation Method 2
introducing to the surface of the particle an organic group having a main structure and a substituent bonding to the main structure, and setting at least one condition of the kind of the substituent, the number of bonds to the main structure and the bonding position, to localize electrons in the main structure to thereby control the charging state of the particle
Data Source
AI summary
There is provided an electrophoretic particle which contains a core material particle formed of a composition containing a resin, a nitrogen-containing heterocyclic compound having any one of an imino group, a methylol group and an alkoxymethyl group in the molecule and a heterocyclic ring having a nitrogen atom, and a coloring agent.