Electrophoretic Particle Polymer Coating for Display Contrast

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional electrophoretic display devices suffer from uneven particle distribution and reduced display quality, particularly in terms of responsiveness and contrast, due to challenges in evenly injecting dispersions and maintaining uniform properties during the injection process.

Innovation Solution

The development of an electrophoretic particle with a pigment particle and a polymer layer, where the average particle diameter is 1 μm or smaller, and the polymer layer has an average thickness of 1 to 500 nm, covering 50% or more of the particle's surface, produced through radical polymerization using a dispersion polymerization method with specific solvent and monomer ratios, enhancing zeta potential and dispersibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If porous spacers are used to dispose between transparent substrates for injecting dispersion, then particle distribution uniformity is improved, but injection difficulty increases and dispersion property stability deteriorates

Engineering Contradiction:

Improveparticle distribution uniformityVSAvoidinjection difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The invention extracts the dispersion injection step entirely by pre-encapsulating electrophoretic particles within microcapsules during manufacturing. This eliminates the need for subsequent injection operations, thereby resolving the contradiction between achieving uniform particle distribution and maintaining ease of manufacture.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention performs preliminary encapsulation of electrophoretic particles in microcapsules before device assembly. This preliminary action ensures uniform particle distribution is achieved during capsule formation rather than during device injection, thereby improving manufacturing precision while maintaining ease of manufacture.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If conventional electrophoretic particles are used, then device simplicity is maintained, but display responsiveness and contrast deteriorate

Engineering Contradiction:

Improveparticle structure simplicityVSAvoiddisplay responsiveness and contrast

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The invention creates composite electrophoretic particles by encapsulating core particles with shell materials within microcapsules. This composite structure enhances display responsiveness and contrast while maintaining reasonable device complexity, as the microcapsule structure is a well-established format in display technology.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention applies local quality enhancement by providing different functional layers within the microcapsule structure - core particles for electrophoretic function and shell materials for enhanced optical properties. This localized functional differentiation improves display responsiveness and contrast without requiring complete structural redesign.

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If polymer layer thickness is increased to improve coating coverage, then surface coverage is improved, but particle mobility deteriorates

Engineering Contradiction:

Improvecoating coverage uniformityVSAvoidparticle mobility

Core Design Contradiction:

Manufacturing precisionVSSpeed

Solution Approach 1:

The invention optimizes the polymer layer thickness parameter within the specific range of 1 to 500 nm to achieve the desired balance. This parameter optimization ensures sufficient coating coverage for stability while maintaining particle mobility for responsive display operation, resolving the contradiction between coverage and mobility.

Inventive Principle:

Principle #35Parameter changes

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 an electrophoretic display device with significantly improved display responsiveness and contrast, ensuring high polymerization rates and uniform polymer coating, leading to enhanced display stability and performance.

Implementation Method 1

carrying out radical polymerization using a polymerization initiator in a state where a pigment particle and monomer components are present in a solvent

Methodology Applied

Scientific EffectRadical polymerization: Photopolymerisation

Implementation Method 2

charged particles dispersed in a liquid migrate in the liquid in response to an external electric field

Methodology Applied

Scientific EffectElectrophoresis: Electrophoresis

Data Source

PatentUS7352502B2Electrophoretic particle, process for its production, and its use

Publication Date: 2008.04.01 E INK CORP

AI summary

An electrophoretic particle including: a pigment particle having an average particle diameter of 1 μm or smaller; and a polymer layer having an average thickness of 1 to 500 nm formed on a surface of the pigment particle, wherein 50% or higher of an entire surface of the pigment particle is coated with the polymer layer. The electrophoretic particle can be produced by radical polymerization using a polymerization initiator in a state where a pigment particle and monomer components are present in a solvent. The electrophoretic particle can be used in a microcapsule and a sheet for electrophoretic display, as well as an electrophoretic display device and an electronic equipment.