Electrochromic Display Particles with Insulating Surface Coating

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Solution Overview

Problem

Electrochromic display devices with organic electrochromic compounds attached to conductive or semi-conductive fine particles suffer from poor image-retaining properties due to charge leakage, which limits their ability to maintain colored states over time, especially when not driven by voltage.

Innovation Solution

Incorporating conductive or semi-conductive fine particles with an insulating or semi-conductive substance attached to their surface, which carry an organic electrochromic compound, to prevent charge leakage and enhance image-retaining properties without increasing the voltage required for color production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If organic electrochromic compounds are attached to conductive or semi-conductive fine particles, then color production efficiency is improved, but image-retaining properties deteriorate due to charge leakage

Engineering Contradiction:

Improvecolor production efficiencyVSAvoidimage-retaining properties

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies composite materials by combining conductive or semi-conductive fine particles with insulating or semi-conductive substances to create a hybrid structure. The insulating substance is attached to the surface of the conductive particles, forming a composite that prevents charge leakage while maintaining color production efficiency. This composite structure resolves the contradiction by integrating both conductive and insulating properties in a single material system.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent implements local quality by applying insulating substances specifically to the surface regions of conductive fine particles where charge leakage occurs. The insulating substance is not uniformly distributed throughout the entire particle but is localized at the surface, allowing the core conductive properties to be preserved while preventing charge leakage at critical interfaces. This localized modification resolves the contradiction without compromising overall color production efficiency.

Inventive Principle:

Principle #3Local quality

2Reliability

If insulating substance is attached to fine particles to prevent charge leakage, then image-retaining properties are improved, but voltage required for color production increases

Engineering Contradiction:

Improveimage-retaining propertiesVSAvoidvoltage for color production

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies parameter changes by carefully controlling the electrical conductivity parameters of the insulating substance. The insulating substance is selected and applied such that its conductivity is not completely insulating but rather semi-conductive or weakly insulating, allowing sufficient charge transport for color production at low voltages while still preventing excessive charge leakage. This parameter optimization resolves the contradiction between image-retaining properties and voltage requirements.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If organic electrochromic compounds are attached to fine particles, then reflective display characteristics are achieved, but white reflectivity is poor

Engineering Contradiction:

Improvereflective display characteristicsVSAvoidwhite reflectivity

Core Design Contradiction:

Ease of manufactureVSIllumination intensity

Solution Approach 1:

The patent introduces an intermediary substance (insulating or semi-conductive material) that mediates between the organic electrochromic compounds and the fine particles. This intermediary layer improves the optical properties by reducing light scattering and absorption at particle interfaces, thereby enhancing white reflectivity while maintaining the reflective display characteristics provided by the electrochromic compounds.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution significantly improves image-retaining properties, allowing the display device to maintain colored states for extended periods without voltage application, while maintaining high white reflectivity and low-voltage operation, enabling efficient and durable color production.

Implementation Method 1

A phenomenon in which electrochromic materials applied with a voltage show a reversible color change during the electrochemical redox reaction is called electrochromism

Methodology Applied

Scientific EffectElectrochromism: Electrochromism

Implementation Method 2

electrochromic materials applied with a voltage show a reversible color change during the electrochemical redox reaction

Methodology Applied

Scientific EffectElectrochemical redox reaction: Redox Reactions

Data Source

PatentUS7525716B2Display device and display apparatus

Publication Date: 2009.04.28 RICOH CO LTD

AI summary

To provide a display device which includes: a display electrode; a counter electrode provided to face the display electrode; a display layer provided on the counter electrode-side surface of the display electrode; and an electrolyte provided between the display electrode and the counter electrode, wherein the display layer comprises conductive or semi-conductive fine particles, the fine particles comprise an insulating or semi-conductive substance attached to the surface thereof, and the fine particles carry an organic electrochromic compound.