Interference Pigments with Broad SiO2 Layer Thickness Distribution
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Solution Overview
Problem
Existing interference pigments based on SiO2 flakes with uniform layer thicknesses face limitations in controlling color change intensity and achieving neutral colors like silver-white, as they often exhibit intense color flop and cannot be used to create subtle color transitions.
Innovation Solution
Developing interference pigments with a broad layer-thickness distribution of SiO2 flakes, coated with high-refractive-index layers, allowing for customizable color flop from pronounced to subtle effects, and enabling the production of neutral colors by mixing flakes with different thicknesses, such as 360 nm to 500 nm, to achieve high tinting strength and color purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If SiO2 flakes with uniform layer thickness are used, then intense interference colours and strong angle-dependent colour-change effects are achieved, but the colour flop cannot be controlled and neutral colors like silver-white cannot be produced
Solution Approach 1:
The patent applies local quality by creating a distribution of different layer thicknesses within the pigment composition. Instead of uniform thickness, flakes with varying thicknesses (creating different optical paths) are combined, allowing different regions of the pigment to contribute different color intensities. This enables control over the overall color flop effect while maintaining intense interference colors from individual flakes.
Solution Approach 2:
The invention uses composite materials by combining SiO2 flakes with different layer thicknesses into a single pigment composition. This composite approach allows the material to exhibit both intense interference colours (from individual flakes) and controlled color transitions (from the distribution of thicknesses), resolving the contradiction between intensity and controllability.
2Quantity of substance
If SiO2 flakes with uniform layer thickness are used, then high tinting strength is achieved, but neutral interference colors like silver-white cannot be obtained
Solution Approach 1:
The patent applies parameter changes by varying the layer thickness parameter across different flakes in the composition. By controlling the distribution of thickness values, the invention can tune the interference effects to produce neutral colors like silver-white while maintaining high tinting strength. The key is changing the thickness parameter from uniform to distributed.
3Adaptability or versatility
If a broad layer-thickness distribution of SiO2 flakes is used, then color flop can be controlled from pronounced to subtle effects, but the complexity of preparing flakes with multiple different thicknesses increases
Solution Approach 1:
The patent applies segmentation by dividing the pigment preparation into discrete thickness categories. Instead of attempting continuous thickness control, the invention segments flakes into distinct thickness groups (e.g., first, second, third thicknesses) that can be independently prepared and then combined. This reduces the complexity of the overall process while achieving the desired color flop control.
4Ease of manufacture
If SiO2 flakes with single layer thickness are used, then manufacturing process is simple, but the pigment exhibits intense color flop that is not always desired
Solution Approach 1:
The patent applies the taking out principle by extracting the excessive color flop effect through the addition of flakes with different thicknesses. The thinner flakes contribute different interference patterns that counterbalance the intense color flop from thicker flakes, effectively extracting or reducing the unwanted intense effect while maintaining the desirable interference colours.
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 allows for precise control of color change, enabling the creation of interference pigments with high gloss and pure-white mass tone, including neutral colors like silver-white, while maintaining high tinting strength and subtle color transitions, suitable for various applications including cosmetics and food products.
Implementation Method 1
interference pigments consist of flake-form substrates which have particle sizes in the range 5-150 μm and are coated with one or more metal oxides, such as, for example, TiO2 or Fe2O3, Fe3O4. The interference pigments have a uniform layer thickness here.
Implementation Method 2
The metal oxide-coated SiO2 flakes on the market with the trade name Xirona® from Merck KGaA consist of SiO2 flakes of uniform thickness covered with a metal-oxide layer (TiO2 or Fe2O3) having a thickness of 10 nm to 500 nm.
Data Source
AI summary
The invention relates to interference pigments based on SiO2 flakes having a broad layer-thickness distribution, and to the use thereof in paints, coatings, powder coatings, plastics and in particular in cosmetic formulations and for colouring food and pharmaceutical products.