Electret Speaker Blended Polymer Charge Storage

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Solution Overview

Problem

Conventional electret speakers face challenges in achieving excellent charge storage stability and fabricating a thin electret-metal-electret structure due to adhesion issues with fluorine-containing polymers and limited charge storage capability of other polymer electrets.

Innovation Solution

A blended polymer solution is used, combining materials like cyclic olefin copolymer (COC) with other polymers and solvents, followed by a corona charge process to enhance surface voltage and charge storage, and forming the electret layer through processes like spraying-coating and roll-to-roll fabrication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fluorine-containing polymers (PTFE, FEP) are used for electret layers, then charge storage capability is improved, but adhesion to metals deteriorates

Engineering Contradiction:

Improvecharge storage capabilityVSAvoidadhesion to metals

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent uses composite materials by combining fluorine-containing polymer particles (for charge storage) with a binder polymer (for adhesion and structural integrity). The binder polymer matrix embeds the fluorine-containing polymer particles, creating a composite electret layer that achieves both excellent charge storage capability and good adhesion to metal electrodes, resolving the contradiction between these two properties.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If other polymer electrets (PS, PC, PVC, PMMA) are used, then adhesion to metals is improved, but charge storage capability deteriorates

Engineering Contradiction:

Improveadhesion to metalsVSAvoidcharge storage capability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention creates a composite electret material where fluorine-containing polymer particles (providing superior charge storage) are dispersed within a binder polymer matrix (providing adhesion and processability). This composite structure allows the system to achieve both good adhesion to metals and excellent charge storage capability, overcoming the limitations of using single polymer materials.

Inventive Principle:

Principle #40Composite materials

3Reliability

If fluorine-containing solutions (CYTOP, Teflon AF 1600) are used, then charge storage capability is improved, but machining property deteriorates

Engineering Contradiction:

Improvecharge storage capabilityVSAvoidmachining property

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the physical state and processing parameters by using a binder polymer system that allows the electret layer to be formed as a flexible coating rather than a rigid solid block. The binder polymer enables the electret layer to be applied to curved surfaces and complex geometries through coating processes, significantly improving machinability and ease of fabrication while maintaining excellent charge storage capability from the fluorine-containing polymer particles.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If conventional electret materials are used, then charge storage stability is improved, but fabrication of thin electret-metal-electret structure becomes difficult

Engineering Contradiction:

Improvecharge storage stabilityVSAvoidfabrication of thin structure

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention changes the processing parameters by using a binder polymer system that enables low-temperature processing and flexible coating methods. This allows for the fabrication of thin electret-metal-electret structures with precise thickness control, as the binder polymer can be applied in thin layers and cured at lower temperatures compared to conventional electret materials, achieving both charge storage stability and manufacturing precision.

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

The blended polymer solution significantly improves charge storage capability and stability, increasing surface voltage by up to 190% and enhancing the electret property, suitable for high-fidelity and low-distortion sound generation.

Implementation Method 1

followed by a corona charge process to enhance surface voltage and charge storage

Methodology Applied

Scientific EffectCorona charge: Corona Discharge

Implementation Method 2

The electret layer is formed from a polymer-containing solution

Methodology Applied

Scientific EffectElectret property: Electret

Implementation Method 3

An electrostatic speaker operates on the principle of Coulomb's law that two conductors with equal and opposite charge may generate a push-pull force between them

Methodology Applied

Scientific EffectElectrostatic force: Coulomb's Law

Data Source

PatentUS8111847B2Electret materials, electret speakers, and methods of manufacturing the same

Publication Date: 2012.02.07 NAT TAIWAN UNIV

AI summary

A speaker comprises at least one electrode electrically coupled with an audio signal input and a film comprising at least one electret layer. The film is configured to interact with the electrode in response to an audio signal supplied by the audio signal input and to vibrate to generate sound waves. The electret layer is formed from a polymer-containing solution.