Stretchable Conductor Sheet Isotropic Conductivity
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Solution Overview
Problem
Conductive compositions used in stretchable conductor sheets face issues with isotropic conductivity, durability against deformation, and resistance changes during elongation, twist, and washing, leading to reduced performance in wearable electronic devices.
Innovation Solution
A stretchable conductor sheet comprising conductive particles, inorganic particles surface-treated with hydroxides or oxides of Al and Si, and a flexible resin with specific elastic modulus, which maintains isotropic conductivity and resistance stability even under repeated deformation and washing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal foil is used to form wiring by etching, then wiring can be formed with low resistance, but the wiring lacks practical stretchability and undergoes permanent plastic deformation when excessively deformed
Solution Approach 1:
The patent changes the physical state and composition parameters of the conductor from solid metal foil to a composite paste containing conductive particles (silver, carbon, etc.) dispersed in a flexible resin matrix. This parameter change enables the conductor to exhibit both electrical conductivity and elastic deformability, resolving the contradiction between low resistance and stretchability
Solution Approach 2:
The patent creates a composite material system combining conductive particles with flexible resin (elastomer) to form a stretchable conductor paste. This composite structure allows the conductor to maintain electrical conductivity through particle networks while the resin matrix provides elastic deformation capability, simultaneously achieving low resistance and practical stretchability
2Adaptability or versatility
If wave-shaped metal wire or foil is arranged to provide pseudo-stretchability, then stretchability is achieved through twist deformation, but the garment has uncomfortable wearing feeling and the metal undergoes permanent plastic deformation
Solution Approach 1:
The patent changes the geometric configuration parameter from fixed wave-shaped structures to a flexible paste that can be printed in various patterns. The paste formulation with conductive particles and elastomer resin allows the conductor to stretch uniformly without creating uncomfortable rigid wave structures, improving wearing comfort while maintaining stretchability
Solution Approach 2:
The patent uses a flexible resin matrix (elastomer) as the continuous phase to embed conductive particles, creating a thin film-like stretchable conductor. This flexible matrix allows the conductor to deform elastically with the garment without permanent deformation, eliminating the uncomfortable wearing feeling associated with rigid wave-shaped metal structures
3Adaptability or versatility
If conductive particles and stretchable binder resin are combined to form stretchable conductor, then the composition has inherent stretchability and flexibility in width and thickness, but the resistivity is higher than metal wires or foil
Solution Approach 1:
The patent optimizes the composite material formulation by selecting appropriate conductive particles (silver, carbon, carbon nanotubes) with high intrinsic conductivity and arranging them in interconnected networks within the resin matrix. This composite structure achieves low resistivity comparable to metal wires while maintaining the stretchability provided by the elastomer resin
Solution Approach 2:
The patent adjusts composition parameters including particle concentration, particle size distribution, and resin type to optimize the balance between conductivity and stretchability. By controlling these parameters, the paste forms a conductor with sufficiently low resistivity for practical applications while retaining elastic deformability
4Reliability
If inorganic particles are added to conductive composition to improve durability, then resistance stability during deformation is improved, but the conductivity may become anisotropic
Solution Approach 1:
The patent uses inorganic particles with surface treatments (hydroxides or oxides of Al and Si) to create localized reinforcement zones within the conductive matrix. These surface-treated particles maintain isotropic distribution while providing local structural stability during deformation, preventing both excessive resistance change and conductivity anisotropy
Data Source
AI summary
A first object of the present invention is to provide a stretchable conductor sheet that exhibits isotropic conductivity when stretched in a predetermined direction or in a direction perpendicular to the predetermined direction, and a paste for forming a stretchable conductor sheet, which is used for the stretchable conductor sheet. A second object of the present invention is to provide a stretchable conductor sheet having a small change in specific resistance even when repeatedly twisted, and a paste for forming a stretchable conductor sheet, which is used for the stretchable conductor sheet. A third object of the present invention is to provide a stretchable conductor sheet having a small change in specific resistance even when repeatedly washed, and a paste for forming a stretchable conductor sheet, which is used for the stretchable conductor sheet. The first object of the present invention can accomplish a stretchable conductor sheet having a thickness of 3 to 800 μm, the stretchable conductor sheet comprising at least conductive particles, inorganic particles surface-treated with a hydroxide and/or an oxide of one or both of Al and Si, and a flexible resin having a tensile elastic modulus of 1 MPa or more and 1000 MPa or less, wherein in each of two orthogonal directions, a specific resistance change ratio of the sheet at a time of elongation by 40% with respect to an original length is less than ±10% in an elongation direction.