Radio Wave Absorber with Flame Retardant Resin Support

Solution Overview

Problem

The existing λ/4 radio wave absorbers have low flexibility and increased weight due to a glass layer, which limits their installation locations and can lead to decreased radio wave absorption performance, and the inclusion of flame retardants in the dielectric layer can adversely affect the resistive and conductive layers, compromising long-term absorption performance.

Innovation Solution

A radio wave absorbing member with a resistive layer, a reflective layer, and a dielectric layer, supported by a sheet-shaped matrix resin containing a flame retardant, which maintains flame retardancy without affecting the resistive or conductive layers, and is designed to absorb radio waves effectively while being lightweight and flexible.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a glass layer is disposed on the surface of a λ/4 radio wave absorber to improve flame retardancy, then the flame retardancy is improved, but the flexibility becomes very low and the weight increases

Engineering Contradiction:

Improveflame retardancyVSAvoidflexibility

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent changes the material parameters of the support layer by incorporating flame retardant particles (such as aluminum hydroxide, magnesium hydroxide, or boron nitride) into the resin matrix. This allows the support layer to achieve flame retardancy without requiring a glass layer, thereby maintaining flexibility and reducing weight while still providing fire protection.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite material structure where flame retardant particles are dispersed within a resin-based support layer. This composite approach combines the benefits of flame retardancy with the flexibility and light weight of polymer materials, eliminating the need for rigid glass layers while maintaining fire safety performance.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If a glass layer is disposed on the surface of a λ/4 radio wave absorber to improve flame retardancy, then the flame retardancy is improved, but the total weight increases

Engineering Contradiction:

Improveflame retardancyVSAvoidweight

Core Design Contradiction:

Object-affected harmful factorsVSWeight of stationary object

Solution Approach 1:

The patent changes the material parameters of the support layer by incorporating flame retardant particles (such as aluminum hydroxide, magnesium hydroxide, or boron nitride) into the resin matrix. This allows the support layer to achieve flame retardancy without requiring a glass layer, thereby maintaining flexibility and reducing weight while still providing fire protection.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses lightweight resin-based support layers with flame retardant additives instead of heavy glass layers. These resin-based solutions are lighter, more cost-effective, and sufficiently durable for the application, replacing the need for heavy protective glass structures.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Object-affected harmful factors

If a flame retardant is included in the dielectric layer to increase flame retardancy, then the flame retardancy is improved, but the resistive layer or electrically conductive layer may be detached or properties may change

Engineering Contradiction:

Improveflame retardancyVSAvoidradio wave absorption performance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent segments the flame retardant function from the dielectric layer and assigns it to a separate support layer. The dielectric layer maintains its original composition and electrical properties, while the support layer provides flame retardancy. This segmentation prevents harmful interactions between flame retardants and the electrical layers, ensuring both fire safety and reliable radio wave absorption performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a dedicated support layer as an intermediary between the external environment and the radio wave absorber structure. This support layer contains the flame retardant and protects the internal dielectric and conductive layers from direct exposure to flame retardant materials, preventing degradation while maintaining fire protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Object-affected harmful factors

If a flame retardant is included in the dielectric layer to increase flame retardancy, then the flame retardancy is improved, but the resistive layer or electrically conductive layer may be detached

Engineering Contradiction:

Improveflame retardancyVSAvoidadhesion

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The patent segments the flame retardant function from the dielectric layer and assigns it to a separate support layer. The dielectric layer maintains its original composition and electrical properties, while the support layer provides flame retardancy. This segmentation prevents harmful interactions between flame retardants and the electrical layers, ensuring both fire safety and reliable radio wave absorption performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a dedicated support layer as an intermediary between the external environment and the radio wave absorber structure. This support layer contains the flame retardant and protects the internal dielectric and conductive layers from direct exposure to flame retardant materials, preventing degradation while maintaining fire protection.

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 maintains long-term radio wave absorption performance, increases flame retardancy, and reduces the weight and rigidity of the absorber, allowing for broader installation options while protecting against external impacts and maintaining absorption efficiency.

Implementation Method 1

a dielectric layer having a thickness of t and a relative permittivity of εr, wherein the wavelength λ0 of a radio wave to be absorbed is determined from the thickness t and the relative permittivity εr according to the following equation: λ0=4t×√εr

Methodology Applied

Scientific EffectQuarter-wavelength interference: Interference

Implementation Method 2

a resistive layer having a sheet resistance of 30 to 500Ω/□

Methodology Applied

Scientific EffectResistive heating: Joule Heating

Implementation Method 3

a reflective layer having a sheet resistance of 0.01 to 10Ω/□

Methodology Applied

Scientific EffectElectromagnetic reflection: Reflection

Data Source

PatentUS11476586B2Radio wave absorbing member, radio wave absorbing structure, and inspection apparatus

Publication Date: 2022.10.18 NITTO DENKO CORP

AI summary

A radio wave absorbing member 1a includes a radio wave absorber 10 and a support 20 having a sheet shape. The radio wave absorber 10 includes a resistive layer 12, a reflective layer 14, and a dielectric layer 13. The reflective layer 14 reflects a radio wave. The dielectric layer 13 is disposed between the resistive layer 12 and the reflective layer 14 in the thickness direction of the reflective layer 14. The support 20 supports the radio wave absorber 10. The support 20 includes a matrix resin 20m and a flame retardant 20p.