Darkening Layer Coating for Vehicle Pane Light Transmittance
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Solution Overview
Problem
Existing thermal radiation reflecting coatings for vehicle windows are prone to production defects, corrosion, and damage during bending and prestressing, leading to high light transmittance and aesthetic issues, especially when attempting to achieve low transmittance levels.
Innovation Solution
A thermal radiation reflecting coating comprising a substrate with a lower dielectric layer, a functional layer containing transparent conductive oxide, an upper dielectric layer, and one or more darkening layers made of metals, metal nitrides, or metal carbides with high melting points and low electrical resistivity, which are corrosion-resistant and maintain performance during temperature treatment, bending, and prestressing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transmittance-reducing thermal radiation reflecting coatings are applied to achieve low light transmittance, then aesthetic requirements and thermal comfort are improved, but layer defects become highly visible and production precision deteriorates
Solution Approach 1:
The patent applies a darkening layer with specific optical properties that absorbs visible light and reflects infrared radiation. This layer is designed to have high absorption in the visible range (reducing transmittance to 5-15%) while maintaining infrared reflectivity for thermal management. The darkening layer's optical characteristics mask the visibility of underlying layer defects by providing a uniform dark appearance that reduces contrast effects.
Solution Approach 2:
The patent uses a composite coating structure consisting of multiple functional layers: a darkening layer (5-20 nm) made of materials like titanium nitride, chromium nitride, or nickel-chromium alloys; a thermal radiation reflecting layer (50-150 nm) with infrared reflectivity >60%; and dielectric layers for adhesion and protection. This composite structure achieves both low visible transmittance and high infrared reflectivity while the combined effect masks production defects.
2Illumination intensity
If transparent conductive oxide coatings are used to maintain transparency, then light transmittance is improved, but achieving very low transmittance (less than 8%) becomes impossible
Solution Approach 1:
The patent divides the coating into functionally separate layers: a darkening layer specifically optimized for visible light absorption (achieving 5-15% transmittance), and a thermal radiation reflecting layer for infrared management. This segmentation allows each layer to be optimized for its specific function, enabling very low visible transmittance while maintaining thermal performance, something transparent conductive oxides alone cannot achieve.
3Loss of energy
If silver-based low-E coatings are applied to achieve high infrared reflectivity, then thermal radiation reflection is improved, but corrosion resistance deteriorates
Solution Approach 1:
The patent introduces dielectric intermediary layers (such as silicon oxide, silicon nitride, or titanium oxide) between the darkening layer and the thermal radiation reflecting layer, and between the reflecting layer and the environment. These dielectric layers act as protective barriers that prevent corrosion of the metallic layers while allowing infrared radiation to be reflected. This intermediary protection enables the use of highly reflective metallic layers without suffering from their inherent corrosion susceptibility.
4Shape
If panes are subjected to bending and prestressing to achieve desired shape, then mechanical transformation is accomplished, but coating damage occurs
Solution Approach 1:
The patent applies the multi-layer coating to the pane surface before bending and prestressing operations. The coating is designed with appropriate layer thicknesses and material selections (including flexible dielectric layers) that allow it to withstand the subsequent thermal and mechanical processing without cracking or delaminating. This preliminary application followed by controlled processing ensures coating integrity while achieving the desired pane shape.
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 visible light transmittance, enhances corrosion resistance, and withstands mechanical transformations, allowing for the production of very dark panes with improved thermal comfort and reduced energy consumption.
Implementation Method 1
The coating contains a darkening layer which reduces the transmittance of the pane in the visible spectral range
Implementation Method 2
Thermal radiation reflecting coatings reflect a significant part of sunlight, in particular in the infrared range
Data Source
AI summary
The present invention relates to a pane with thermal radiation reflecting coating, comprising a substrate (1) and at least one thermal radiation reflecting coating (2) on at least one of the surfaces of the substrate (1), wherein the coating (2), proceeding from the substrate (1), comprises at leastone lower dielectric layer (3),one functional layer (4) that contains at least one transparent, electrically conductive oxide, andone upper dielectric layer (5),and wherein at least one darkening layer (10) is arranged below the lower dielectric layer (3), between the lower dielectric layer (3) and the functional layer (4), between the functional layer (4) and the upper dielectric layer (5), and/or above the upper dielectric layer (5),and wherein the darkening layer (10) contains at least one metal, one metal nitride, and/or one metal carbide with a melting point greater than 1900° C. and a specific electrical resistivity less than 500 μohm*cm.