Shaped Silver Particle Coatings for Angle-Dependent Color Shift
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Solution Overview
Problem
Existing security elements and holograms lack an effective method to achieve angle-dependent color change, strong rainbow effects, and high contrast, which are essential for advanced security features in documents and products.
Innovation Solution
The use of shaped transition metal particles, such as silver, copper, or gold, with a binder in specific ratios to create coatings that exhibit color shifting effects, allowing for angle-dependent color changes and enhanced optical variable effects, including strong rainbow effects and high contrast, without the need for additional colorants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional coating compositions are used for security elements, then the production process is simple, but the angle-dependent color change and rainbow effect are insufficient
Solution Approach 1:
The patent changes the physical and chemical parameters of the coating composition by incorporating specific shaped transition metal particles (silver, copper, or gold) with controlled aspect ratios (5:1 to 50:1) and specific surface area ranges (0.5 to 5 m²/g). These parameter changes enable the coating to exhibit angle-dependent color changes and strong rainbow effects while maintaining a relatively simple production process.
Solution Approach 2:
The patent creates a composite coating material by combining shaped transition metal particles with a binder in specific ratios (0.1 to 10 parts binder per part pigment). This composite structure integrates the optical properties of the metal particles with the adhesive and protective properties of the binder, achieving both enhanced visual effects and coating stability.
2Adaptability or versatility
If additional colorants are added to achieve color variation, then the color range is improved, but the purity and contrast are reduced
Solution Approach 1:
The patent utilizes the inherent color-changing properties of shaped transition metal particles through optical interference and light scattering effects. By controlling particle shape, size, and arrangement, the coating naturally exhibits angle-dependent color changes without requiring additional colorants, thereby maintaining high color purity and contrast.
Solution Approach 2:
The patent extracts and eliminates additional colorants from the coating composition, relying solely on the optical properties of the shaped transition metal particles. This extraction of unnecessary components preserves the purity and contrast of the color effects while achieving the desired color variation through physical rather than chemical means.
3Illumination intensity
If the pigment to binder ratio is increased to enhance optical effects, then the color intensity is improved, but the coating stability and adhesion deteriorate
Solution Approach 1:
The patent optimizes the pigment to binder ratio within the specific range of 0.1 to 10 parts binder per part pigment, and controls the particle characteristics (aspect ratio 5:1 to 50:1, specific surface area 0.5 to 5 m²/g). These parameter optimizations ensure sufficient color intensity and brightness while maintaining adequate binder content for coating stability and adhesion to the substrate.
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 coatings demonstrate significant angle-dependent color change, providing enhanced security features with extremely bright optically variable designs and strong rainbow effects, suitable for use in security documents and products to prevent counterfeiting.
Implementation Method 1
the resulting coating shows an angle dependent colour change
Implementation Method 2
different colours in reflection and transmission
Implementation Method 3
an extremely bright OVD image
Data Source
Figure 1
AI summary
The present invention relates to the use of coating compositions, comprising shaped transition metal, especially silver, particles and a binder, wherein the ratio of pigment to binder is preferably such that the resulting coating shows an angle dependent colour change, for the production of security elements and holograms. When the coating compositions of the present invention are used in coating a hologram the obtained products show a an angle dependent colour change (flip/flop effect), different colours in reflection and transmission, an extremely bright OVD image and extremely strong rainbow effect, high purity and contrast.