Cholesteric Liquid Crystal Heat Shield for Automotive Glass
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Solution Overview
Problem
Windowpanes for automobiles require high visible light transmittance and effective solar radiation heat shielding without causing radio disturbance, as existing solutions like metallic films and IR-absorbing dyes either block electromagnetic waves or suffer from low heat-shielding capabilities.
Innovation Solution
A heat shield comprising a first light-reflective layer of fixed cholesteric liquid-crystal phase reflecting either right- or left-polarized components, and a second layer with organic or inorganic materials, achieving reflectance peaks in specific wavelength ranges to ensure high solar radiation heat shielding while maintaining visible light transmittance and avoiding radio interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metallic film is used for heat shielding, then heat-shielding capability is improved, but radio disturbance occurs and visible light transmittance is reduced
Solution Approach 1:
The patent replaces metallic films with a dielectric multilayer film structure that uses optical interference rather than electrical conductivity to achieve heat shielding. The dielectric layers create constructive and destructive interference patterns that reflect infrared radiation while allowing radio waves to pass through, eliminating the radio disturbance problem inherent in metallic films.
Solution Approach 2:
The patent employs a composite multilayer structure consisting of alternating high-refractive-index and low-refractive-index dielectric layers. This composite structure enables selective wavelength reflection through interference effects, achieving heat shielding in the infrared range while maintaining transparency to visible light and radio waves.
2Temperature
If a metallic film is used for heat shielding, then heat-shielding capability is improved, but visible light transmittance is reduced
Solution Approach 1:
The patent applies local quality by designing the dielectric multilayer film to have different optical properties at different wavelength ranges. The layer thicknesses and refractive indices are specifically optimized to reflect infrared radiation (heat shielding) while being transparent to visible light, achieving wavelength-selective optical properties.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the thickness of individual dielectric layers and their refractive indices to control the interference pattern. By optimizing these parameters, the film reflects infrared wavelengths while transmitting visible wavelengths, resolving the contradiction between heat shielding and visible light transmittance.
3Temperature
If a birefringent multilayer dielectric film is used, then reflectivity in near-infrared range is improved, but reflection at around 400 nm increases causing color shift
Solution Approach 1:
The patent uses parameter changes by precisely controlling the thickness of each dielectric layer to tune the interference pattern. The layer thicknesses are optimized to create reflection bands in the infrared range while maintaining minimal reflection in the visible range (including 400 nm), preventing color shift while achieving high infrared reflectivity.
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 provides effective solar radiation heat shielding with high visible light transmittance and minimal radio disturbance, meeting safety and communication instrument compatibility standards, and is cost-effective by avoiding costly vacuum deposition processes.
Implementation Method 1
a first light-reflective layer comprising at least one layer formed of a fixed cholesteric liquid-crystal phase, and reflecting either a right-polarized component or a left-polarized component
Implementation Method 2
reflecting at least one of a right-polarized component and a left-polarized component
Implementation Method 3
effective for reducing heat load due to sunlight... prevent transmission of sunlight rays falling within any of the visible range or the infrared range
Data Source
AI summary
A heat shield comprising a first light-reflective layer, having a reflectance peak both in a wavelength range of from 400 nm to less than 850 nm and in a wavelength range of from more than 850 nm to 1300 nm and satisfying C>A>B, is disclosed. “A” means the maximum reflectance in the wavelength range of from 400 nm to less than 850 nm; “B” means the reflectance at a wavelength of 850 nm; “C” means the maximum reflectance in the wavelength range of from more than 850 nm to 1300 nm; and “B” is equal to or less than 50%.