Dielectric Solar-Control Films for NIR Rejection Without RF Blocking
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Solution Overview
Problem
Current solar control films based on reflective technology are not compatible with radio-frequency transmissions from electronic devices due to RF signal blocking, and dielectric solar control films have limited NIR reflection bandwidth and undesirable visible light reflection at wide angles.
Innovation Solution
Infrared-reflecting films with a first dielectric stack and a second dielectric stack, each comprising alternating layers of high and low refractive index materials, where one layer is an odd multiple and another is an even multiple of the equal optical thickness, creating a wider reflection band centered at 800-1500 nm and allowing RF signals to pass through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If metal-based reflective solar control films are used, then solar energy rejection performance is improved, but RF signal compatibility deteriorates due to RF signal blocking
Solution Approach 1:
The patent extracts the harmful RF-blocking property from metal-based reflective films by replacing metal layers with dielectric materials. The invention uses dielectric solar control films that achieve solar energy rejection through selective absorption and reflection mechanisms that do not involve continuous metal pathways, thereby eliminating RF signal blocking while maintaining solar control performance
Solution Approach 2:
The patent changes the material parameter from metal to dielectric, fundamentally altering the electromagnetic interaction properties. By using dielectric materials with specific refractive indices and thicknesses, the film achieves solar energy rejection through optical interference and absorption mechanisms that are transparent to RF signals, thus changing the electromagnetic parameter profile to eliminate RF blocking
2Object-affected harmful factors
If dielectric solar control films with narrowband IR reflection are used, then RF signal compatibility is improved, but solar energy rejection performance deteriorates due to limited NIR reflection bandwidth
Solution Approach 1:
The patent segments the solar control function into multiple dielectric layers with different optical properties. Each layer is designed with specific thickness and refractive index to contribute to reflection at different wavelengths within the NIR range. This segmentation allows the film to achieve broadband solar energy rejection while maintaining RF compatibility, as each dielectric layer independently contributes to the overall reflection spectrum without creating continuous metal pathways
Solution Approach 2:
The patent employs composite dielectric structures combining multiple materials with different refractive indices (e.g., high-index dielectric layers alternating with low-index dielectric layers). This composite architecture creates multiple optical interfaces that collectively provide broadband NIR reflection through constructive interference, achieving enhanced solar energy rejection while maintaining RF signal compatibility through the absence of metal components
3Ease of manufacture
If dielectric IRR with quarter-wave stack are used, then manufacturing simplicity is improved, but reflection band width is limited and visible light transmission is reduced at wide angles
Solution Approach 1:
The patent extends the reflection band width by incorporating multiple dielectric stacks arranged in sequence, effectively adding a dimensional aspect to the optical interference design. Each stack is tuned to reflect at specific wavelengths, and their combined effect creates a broadband reflection spectrum that maintains performance across wide viewing angles. This multi-stack arrangement provides angular insensitivity while preserving manufacturing feasibility through standard dielectric deposition processes
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 30% reflection of electromagnetic waves in the NIR range, 85% transmission of RF wavelengths, and maintain high visible light transmission, addressing compatibility issues with electronic devices and improving solar energy rejection.
Implementation Method 1
alternating layers of high and low refractive index materials of equal optical thickness... causing a double peak reflection band that is wider than the reflection band of the first dielectric reflector stack
Implementation Method 2
The infrared-reflecting films of the invention may reflect at least 30% of electromagnetic waves over a wavelength range, for example, from 850 nm to 1500 nm
Implementation Method 3
The infrared-reflecting films of the invention may transmit at least 85% of radio frequency wavelengths
Data Source
AI summary
Solar-control films are disclosed that include a first dielectric stack having: alternating layers of high and low refractive index materials of a first equal optical thickness; and at least one layer that is an odd multiple of the first equal optical thickness, wherein the first dielectric stack has a reflection band centered at a wavelength from 800 nm to 1500 nm; and a second dielectric stack, optically adjacent the first dielectric stack, having: alternating layers of high and low refractive index materials of a second equal optical thickness; and at least a single layer that is an even multiple of the second equal optical thickness.