Electret Filter Sheet Lamination for Charge Recovery After Cleaning
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Solution Overview
Problem
Electret filters experience a decrease in dust collection capability after cleaning due to loss of electric charge, leading to reduced filtration efficiency and pressure loss.
Innovation Solution
An electret-treated sheet with a specific laminated structure, featuring a high dielectric layer between the surface and back-surface layers, which helps recover surface potential and maintain dust collection efficiency even after cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If the filter is cleaned by washing with water to remove dust, then the filter can be reused, but the electric charge on the surface vanishes and dust collection capability is lowered
Solution Approach 1:
The electret-treated sheet is divided into multiple functional layers: surface layers (with low dielectric constant) that maintain charge and a high dielectric layer (with high dielectric constant) that recovers charge after cleaning. This segmentation allows different layers to perform different functions - the surface layers provide stable electrostatic charge for dust collection, while the high dielectric layer acts as a charge reservoir that replenishes the surface layers after water cleaning
Solution Approach 2:
The sheet combines multiple materials with different dielectric properties into a composite structure. The surface layers use materials with low dielectric constants (e.g., polyolefin) to maintain electrostatic charge, while the high dielectric layer uses materials with high dielectric constants (e.g., barium titanate, lead zirconate titanate) to store and recover charge. This composite structure enables the filter to maintain dust collection capability after cleaning by allowing charge transfer from the high dielectric layer to the surface layers
2Reliability
If a water-resistant coating is applied to maintain charge after cleaning, then charge retention is improved, but the coating causes static charge repulsion in printing and discharge damage in semiconductor fields
Solution Approach 1:
The sheet has different dielectric properties in different regions/layers: the surface layers have low dielectric constants to minimize static charge effects and allow charge dissipation, while the high dielectric layer in the middle has high dielectric constant to provide charge storage. This local quality differentiation allows the surface to be safe for electronic applications while the internal structure maintains charge retention through the high dielectric layer's charge recovery mechanism
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 electret-treated sheet effectively recovers surface potential and maintains high dust collection efficiency with low pressure loss, ensuring effective filtration after cleaning.
Implementation Method 1
the high dielectric layer is a material which has a relative dielectric constant of 6 or larger at 100 kHz
Implementation Method 2
adsorbing dust and dirt by an electrostatic force when air containing dust and dirt passes through the cavity
Data Source
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AI summary
An object of the present invention is to provide a low pressure-loss type of filter which has a high dust collecting capability and suppresses the lowering of the dust collecting capability even after cleaning. The present invention relates to an electret-treated sheet including at least a surface layer, a high dielectric layer and a back-surface layer, while having the high dielectric layer between the surface layer and the back-surface layer, wherein the surface layer and the back-surface layer are each a thermoplastic resin film having a relative dielectric constant of smaller than 6 at 100 kHz; the high dielectric layer is a material having a relative dielectric constant of 6 or larger at 100 kHz; and the surface layer and the back-surface layer each have a static charge due to electrostatically charge; and to a filter using the same.