Electroconductive Paste for Wearable Circuits

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Solution Overview

Problem

Existing electroconductive pastes for wearable devices lack expansion and contraction durability and require multiple layers for circuit formation, which complicates the manufacturing process and printability, especially when used in clothing that expands and contracts with the body.

Innovation Solution

An electroconductive paste comprising a binder, silver powder, crosslinked resin particles with a glass transition temperature of 35° C. or lower, and an organic solvent, which allows for single-layer circuit formation with excellent expansion and contraction durability through screen printing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If an aqueous dispersion is used in the electroconductive paste, then the paste can be applied, but the printability in screen printing deteriorates compared to organic solvent-based paste

Engineering Contradiction:
Improveapplicability of pasteVSAvoidprintability in screen printing
Core Design Contradiction:
Ease of manufactureVSEase of operation

Solution Approach 1:

The patent changes the solvent parameter from aqueous to organic solvent, which fundamentally alters the paste's rheological properties and compatibility with screen printing processes, thereby improving printability while maintaining ease of manufacture

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite paste formulation combining organic solvent with specific binder resins and conductive particles, optimizing the material composition to achieve both ease of manufacture and superior printability characteristics

Inventive Principle:
Principle #40Composite materials

2Reliability

If multiple layers are formed using the electroconductive paste, then circuit functionality can be achieved, but the number of circuit forming steps increases

Engineering Contradiction:
Improvecircuit functionalityVSAvoidnumber of circuit forming steps
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges multiple functional layers into a single integrated electroconductive paste formulation, combining conductive particles, binder resins, and flexible agents in one material system that can form complete circuit patterns in a single printing step, thereby reducing the number of circuit forming steps while maintaining circuit functionality

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The electroconductive paste is designed with multi-functionality, serving simultaneously as the conductive layer, flexible layer, and adhesive layer, eliminating the need for separate application steps for each function and simplifying the overall circuit forming process

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If the electroconductive paste is used in wearable devices that expand and contract, then the device can conform to body movement, but the electric resistance increases after repeated expansion and contraction

Engineering Contradiction:
Improveconformity to body movementVSAvoidelectric resistance stability
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent changes the glass transition temperature parameter of the binder resin to 35°C or lower, which fundamentally alters the material's mechanical properties, enabling it to remain flexible and maintain low electric resistance even after repeated expansion and contraction cycles

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent develops a composite paste formulation incorporating flexible agents and specific binder resins with low glass transition temperature, creating a material system that maintains both adaptability to body movement and stability of electric resistance under dynamic conditions

Inventive Principle:
Principle #40Composite materials

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 paste maintains high conductivity and flexibility, preventing significant increases in electric resistance even after repeated expansion and contraction, thus enhancing the durability and performance of wearable device circuits.

Implementation Method 1

crosslinked resin particles (C) having a glass transition temperature of 35° C. or lower

Methodology Applied
Scientific EffectGlass transition temperature:

Data Source

PatentUS11421116B2Electroconductive paste
Publication Date: 2022.08.23 FUJIKURA KASEI CO LTD

AI summary

An electroconductive paste according to the present invention contains a binder (A), a silver powder (B), crosslinked resin particles (C) having a glass transition temperature of 35° C. or lower, and an organic solvent (D).