Metallic Luster Pigments with SiO2 Interlayer for Safety
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Solution Overview
Problem
Existing metallic luster pigments have limitations in hiding power and safety properties, particularly in automotive paints, where thinner paint layers are desired and aluminum-based pigments can be flammable and explosive, posing occupational safety risks.
Innovation Solution
Development of metallic luster pigments with coated aluminum substrate plates, where the aluminum substrate has a thickness of 5 to 30 nm, coated with a monolithic structure, and covered by a SiO2 layer and a high-refractive index metal oxide layer, such as Fe2O3, with a specific molar ratio of oxygen to aluminum to reduce reactivity and enhance hiding power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If aluminum-based metallic luster pigments are used, then attractive optical effects and color flop are achieved, but flammability and explosiveness increase posing occupational safety risks
Solution Approach 1:
A SiO2 intermediate layer is introduced between the aluminum substrate and the Fe2O3 coating. This intermediary layer prevents direct contact between aluminum and iron oxide, eliminating the thermite reaction hazard while preserving the optical interference effects that create the metallic luster and color flop.
Solution Approach 2:
The pigment is constructed as a composite material system with multiple layers: aluminum substrate, SiO2 intermediate layer, and Fe2O3 outer coating. This composite structure combines the optical properties of aluminum with the safety and color properties of iron oxide, creating a material that exhibits metallic luster without the flammability hazards of pure aluminum-based pigments.
2Quantity of substance
If conventional pigment thickness is used, then sufficient opacity is achieved, but coating layer thickness increases which is undesirable for automotive applications
Solution Approach 1:
The optical properties of the pigment are optimized by precisely controlling the thickness parameters of each layer. The SiO2 layer thickness and Fe2O3 coating thickness are adjusted to achieve maximum opacity and color intensity with minimal total coating thickness, enabling thinner automotive paint layers while maintaining sufficient hiding power.
Solution Approach 2:
Different layers of the pigment structure are optimized for different functions: the aluminum substrate provides the base optical effect, the SiO2 intermediate layer controls light refraction and interference, and the Fe2O3 outer coating enhances color saturation and opacity. This local optimization of each layer's properties achieves high opacity with reduced overall thickness.
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 resulting pigments achieve high hiding power with a low color difference and reduced reactivity, ensuring safety by minimizing flammability and explosiveness, making them suitable for automotive and other applications.
Implementation Method 1
Such metallic luster pigments, which are generally based on platelet-shaped substrates with at least a single coating, exhibit interference effects due to the superposition of differently refracted and reflected light rays. White light incident on the flat surface of the coated substrate is partially reflected by the outer surface of the coating. The other part is refracted and reflected and refracted again at interfaces, for example between the coating and the substrate surface. This results in the superposition of light rays of different phases. Interference of the reflected light creates a color impression.
Implementation Method 2
The other part is refracted and reflected and refracted again at interfaces, for example between the coating and the substrate surface.
Implementation Method 3
White light incident on the flat surface of the coated substrate is partially reflected by the outer surface of the coating.
Data Source
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AI summary
The invention relates to metallic lustre pigments, to a method for the production thereof, and to the use of metallic lustre pigments of this type.