Selective NIR-Absorbing Coatings for Retroreflective Substrates
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Solution Overview
Problem
Autonomous vehicles face challenges in accurately detecting the size and position of retroreflective substrates due to excessive near-infrared (NIR) electromagnetic radiation reflection, leading to system saturation and inaccurate navigation.
Innovation Solution
A coating composition comprising a resin and pigments like zinc oxide, alumina, antimony tin oxide, tungsten oxide, gold nanoparticles, and others, which absorb and/or scatter electromagnetic radiation in the NIR range, reducing NIR retroreflectance while maintaining sufficient visible retroreflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If retroreflective substrate is used to enhance visibility, then visible retroreflectance is improved, but NIR retroreflectance becomes excessive causing system saturation
Solution Approach 1:
The patent applies local quality by making the coating's optical properties wavelength-dependent. The coating selectively absorbs NIR radiation (800-2000 nm) while maintaining high visible retroreflectance (400-700 nm), creating different functional properties for different parts of the electromagnetic spectrum on the same surface. This is achieved through pigments with specific absorption characteristics in the NIR range.
Solution Approach 2:
The patent utilizes color changes by incorporating pigments that exhibit selective absorption in the NIR region. These pigments appear transparent or colored in the visible range but strongly absorb NIR radiation, effectively changing the optical properties of the coating based on the wavelength of incident light. This allows the coating to appear retroreflective to visible light while being absorptive to NIR.
2Object-affected harmful factors
If coating with NIR absorbing pigments is applied, then NIR retroreflectance is reduced, but visible retroreflectance may be compromised
Solution Approach 1:
The patent employs composite materials by combining retroreflective substrates with coatings containing NIR-absorbing pigments dispersed in a resin matrix. This composite structure integrates the high visible retroreflectance of the substrate with the NIR absorption capability of the pigment-coating layer, achieving both functions simultaneously without compromising either performance.
Solution Approach 2:
The patent applies parameter changes by carefully controlling the concentration, particle size, and distribution of NIR-absorbing pigments in the coating formulation. By optimizing these parameters, the coating achieves sufficient NIR absorption (absorbance ≥0.1 at 905 nm, ≥0.2 at 1550 nm) while maintaining adequate visible retroreflectance for safety applications.
3Ease of manufacture
If uniform coating is applied over retroreflective substrate, then manufacturing simplicity is improved, but non-uniform absorption may occur
Solution Approach 1:
The patent applies copying by using a clear or translucent coating formulation that replicates the retroreflective properties of the underlying substrate while adding NIR absorption capability. The coating acts as a transparent layer that copies the substrate's visible retroreflectance pattern while introducing selective NIR absorption, maintaining manufacturing simplicity without requiring complex multi-layer structures.
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 coating effectively reduces NIR retroreflectance by up to 99% while maintaining visible retroreflectance, enabling accurate detection and navigation by autonomous vehicles.
Implementation Method 1
The pigment is suitable to absorb and/or scatter electromagnetic radiation in a wavelength range of 800 nm to 2000 nm
Implementation Method 2
The pigment is suitable to absorb and/or scatter electromagnetic radiation in a wavelength range of 800 nm to 2000 nm
Data Source
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AI summary
A coating composition for application over a retroreflective substrate, a retroreflective article comprising a coating formed from the coating composition, and a method of production thereof are provided. The coating composition comprises a pigment suitable to absorb and/or scatter electromagnetic radiation in a wavelength rance of 800 nm to 2000 nm. The coating comprises a ratio of reduction in electromagnetic radiation retroreflectance at a wavelength of 905 nm and/or 1550 nm to reduction in electromagnetic radiation retroreflectance averaged over a wavelength range of 400 nm to 700 nm of at least 2:1.