Dielectric Solar-Control Films for RF-Compatible NIR Reflection

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Solution Overview

Problem

Current solar control films face challenges in achieving high visible light transmission and compatibility with radio-frequency transmissions while effectively reflecting infrared energy, particularly at wide viewing angles, and existing dielectric reflectors have limited reflection bandwidth and undesirable visible light reflection.

Innovation Solution

Infrared-reflecting films with a dielectric stack comprising alternating layers of high and low refractive index materials, including layers that are multiples of the equal optical thickness, creating multiple peak reflection bands in the NIR range, and a solar-absorber layer to enhance transmission and reflection properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If metal-based reflectors (silver layers) are used to achieve high solar reflection performance, then solar energy rejection is improved, but RF signal compatibility deteriorates due to signal blocking

Engineering Contradiction:

Improvesolar energy rejectionVSAvoidRF signal blocking

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the harmful RF blocking property from the solar reflection function by replacing metal layers with dielectric materials. The dielectric stack provides solar reflection through optical interference without the electrical conductivity that blocks RF signals, thus separating these two functions.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses alternative dielectric materials (such as silicon nitride, silicon oxide, titanium oxide) that can be deposited as thin films and provide the required solar reflection without the need for thick metal layers, achieving the function with a simpler, more RF-transparent structure.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Loss of energy

If dielectric IRR with quarter-wave stack are used to achieve NIR reflection, then infrared reflection is improved, but visible light transmission deteriorates due to narrow reflection band and significant visible light reflection at wide angles

Engineering Contradiction:

Improveinfrared reflectionVSAvoidvisible light transmission

Core Design Contradiction:

Loss of energyVSIllumination intensity

Solution Approach 1:

The patent divides the dielectric stack into multiple segments (layers) with alternating high and low refractive indices, where each layer is optimized for specific wavelength ranges. This segmentation allows independent optimization of NIR reflection and visible light transmission properties.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different layers of the dielectric stack are designed with specific refractive indices and thicknesses to provide different optical functions: some layers are optimized for NIR reflection while others are optimized for visible light transmission, creating local quality variations throughout the stack.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If additional interference stack is added to extend NIR reflection range, then infrared reflection bandwidth is improved, but visible light transmission deteriorates due to second order peaks causing narrow transmission band

Engineering Contradiction:

Improveinfrared reflection bandwidthVSAvoidvisible light transmission bandwidth

Core Design Contradiction:

Loss of energyVSIllumination intensity

Solution Approach 1:

The patent uses a dielectric stack configuration that dynamically adjusts optical interference patterns based on wavelength. The alternating layer structure creates constructive interference for NIR wavelengths while maintaining destructive interference for visible light, achieving wide NIR reflection without compromising visible transmission.

Inventive Principle:

Principle #15Dynamics

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 films achieve at least 50% visible light transmission and reflect at least 30% of electromagnetic waves in the NIR range, with improved solar energy rejection and compatibility with electronic devices.

Implementation Method 1

a dielectric stack layer comprising alternating layers of high and low refractive index materials of a first equal optical thickness; and at least one layer, or a single layer, that is a multiple of the first equal optical thickness, causing a multiple peak reflection band

Methodology Applied

Scientific EffectOptical interference: Interference

Implementation Method 2

a solar-absorber layer comprising a substrate and solar control particles, laminated to the dielectric stack layer

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Data Source

PatentUS20250237794A1High-performance signal-friendly solar-control films

Publication Date: 2025.07.24 EASTMAN PERFORMANCE FILMS LLC

AI summary

Solar-control films are disclosed that include a first dielectric stack layer comprising: alternating layers of high and low refractive index materials of a first equal optical thickness; and at least one layer that is a multiple of the first equal optical thickness, causing a multiple peak reflection band that exhibits multiple peaks within a wavelength range from about 800 nm to about 1500 nm; and a solar-absorber layer, comprising a substrate and solar control particles, optically adjacent the dielectric stack layer.