Dark Multi-Layer Coating NIR Reflection
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Solution Overview
Problem
Dark-color coatings absorb near-infrared radiation, causing substrates to heat up, which is undesirable, especially in applications like motor vehicles, where it increases the need for air-conditioning fuel consumption.
Innovation Solution
A multi-layer coating process involving an NIR-opaque coating layer A′ with low NIR absorption, followed by a coating layer B′ containing 50-100% black pigments with low NIR absorption, to minimize substrate heating, achieved by using specific pigment compositions and application methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dark-color pigments (carbon black) are used in coating, then color darkness is improved, but substrate heating increases
Solution Approach 1:
The coating is divided into multiple layers with different functions: a lower layer containing carbon black for color darkness, and an upper layer containing aluminum flake pigments for NIR reflection. This segmentation allows each layer to perform its specific function without interfering with the other, resolving the contradiction between color darkness and substrate heating.
Solution Approach 2:
The aluminum flake pigment layer acts as an intermediary between the sunlight and the carbon black layer. It reflects NIR radiation before it reaches the carbon black layer, preventing heat generation while allowing the carbon black layer to maintain its color-darkening function.
2Temperature
If aluminum flake pigments are used to reduce NIR absorption, then substrate heating is reduced, but color darkness may be compromised
Solution Approach 1:
The coating is divided into multiple layers with different functions: a lower layer containing carbon black for color darkness, and an upper layer containing aluminum flake pigments for NIR reflection. This segmentation allows each layer to perform its specific function without interfering with the other, resolving the contradiction between color darkness and substrate heating.
Solution Approach 2:
The invention combines two pigment types with opposing properties (carbon black for darkness, aluminum flake for NIR reflection) into a single multi-layer coating system. By merging their functions in a layered structure, the coating achieves both color darkness and low NIR absorption simultaneously.
3Temperature
If multi-layer coating process is used with specific pigment compositions, then NIR absorption is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent specifies predetermined pigment compositions and layer structures that can be applied using standard coating processes. By establishing the pigment ratios and layer configurations in advance, the complex multi-layer structure can be manufactured efficiently without requiring complex real-time control during production.
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 process results in dark-color multi-layer coatings that heat up minimally in sunlight, reducing the need for air-conditioning fuel in vehicles and maintaining desired color characteristics.
Implementation Method 1
NIR-opaque coating layer which exhibits low NIR absorption
Implementation Method 2
carbon black pigments which absorb radiation in the near-infrared wavelength range and transform it into heat
Implementation Method 3
The pigment content of coating composition A consists 90 to 100 wt. % of at least one aluminum flake pigment
Data Source
AI summary
A process for the production of a dark-color multi-layer coating, comprising the successive steps:(1) applying an NIR-opaque coating layer A′ from a pigmented, solvent- or waterborne coating composition A to a substrate,(2) applying a coating layer B′ from a pigmented coating composition B onto the substrate provided with coating layer A′,wherein the pigment content of coating composition A consists 90 to 100 wt. % of at least one aluminum flake pigment and 0 to 10 wt. % of at least one further pigment, which is selected in such a way that NIR-opaque coating layer A′ exhibits low NIR absorption,wherein the pigment content of coating composition A comprises <90 wt. % of 10 to 80 nm thick aluminum flake pigments,wherein the pigment content of coating composition B consists 50 to 100 wt. % of at least one black pigment with low NIR absorption and 0 to 50 wt. % of at least one further pigment, which is selected in such a way that coating layer B′ exhibits low NIR absorption and that the dark-color multi-layer coating exhibits a brightness L* (according to CIEL*a*b*, DIN 6174), measured at an illumination angle of 45 degrees to the perpendicular and an observation angle of 45 degrees to the specular, of at most 10 units,wherein the sum of the respective wt. % equals 100 wt. %, andwherein the coating layers A′ and B′ are cured.