Plasmonic Security Element Structure for Diffuse-Light Image Stability
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Solution Overview
Problem
Conventional security elements using diffractive optically variable effects suffer from noise under diffuse lighting conditions and misregistration of colors due to separate print processes, lacking precise optical variability and angular stability.
Innovation Solution
A security element utilizing plasmonic nanostructures arranged in differently inclined sub-regions to display distinct images at different viewing angles, leveraging surface plasmon polariton resonance for subtractive color generation, ensuring optical invariability and precise registration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If diffractive optically variable effects are used to generate security elements, then optical variability is achieved, but noise appears under diffuse lighting conditions
Solution Approach 1:
The patent changes the fundamental optical mechanism from diffraction to surface plasmon polariton resonance. This parameter change in the physical effect enables color generation that is insensitive to diffuse lighting conditions while maintaining optical variability through angular dependence of the plasmonic resonance
Solution Approach 2:
The security element divides the surface into multiple sub-regions with different average inclinations. Each sub-region locally generates a specific color through plasmonic resonance at its characteristic angle, creating a noise-free optically variable effect where each local area contributes to the overall angular-dependent color display
2Adaptability or versatility
If printed inks are used to generate optically variable effects, then multiple colors can be produced, but misregistration occurs between different colors
Solution Approach 1:
The patent merges the generation of multiple colors into a single manufacturing process by using plasmonic nanostructures with different geometries or materials that resonate at different angles. All color information is encoded in one layer, eliminating the need for multiple printing steps and ensuring perfect registration between colors
Solution Approach 2:
Instead of generating color variation through multiple printed layers (vertical stacking), the patent uses angular dimension to differentiate colors. Each color is assigned to a specific viewing angle range through plasmonic resonance, allowing all colors to coexist in a single layer without registration issues
3Manufacturing precision
If diffractive structures are used to create security elements, then integral register between structures is achieved, but the security element appears noisy under diffuse lighting
Solution Approach 1:
The patent fundamentally changes the optical mechanism from diffraction to surface plasmon polariton resonance. This parameter change eliminates the noise problem under diffuse lighting while preserving the ability to create integral register between structures through single-process fabrication of plasmonic nanoarrays
4Ease of manufacture
If conventional security elements are used, then ease of manufacture is maintained, but optical invariability and precise angular stability are lacking
Solution Approach 1:
The patent changes the optical mechanism to surface plasmon polariton resonance, which provides inherent angular stability and optical invariability. The plasmonic resonance frequency is determined by the nanostructure geometry and material properties, creating reliable and repeatable optical responses that are insensitive to manufacturing variations
Solution Approach 2:
The patent creates a dynamic optical response where the displayed color changes systematically with viewing angle. The surface is divided into sub-regions with different inclinations, each displaying its color at a specific angle range, creating a controlled dynamic effect that is reliable and repeatable
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 provides optically variable security elements with stable color presentation across angles, enabling complex animations, image switches, and apparent object rotations, enhancing authentication and visual complexity without noise under diffuse lighting.
Implementation Method 1
structures that generate colour from the resonant interactions between light and metallic nanostructures where collective free-electron oscillations within the metallic nanostructure couple to electromagnetic fields in a neighbouring dielectric material
Implementation Method 2
The first surface is arranged such that each sub-region has a respective average inclination and wherein the average inclinations of the first sub-regions are such that the first image is displayed at least at a first viewing angle
Data Source
AI summary
A security element including a first layer having a first surface, an array of image regions across the surface, each including at least first and second sub-regions, a first array of plasmonic nanostructures in or on the surface across the first sub-regions, defining in each a corresponding portion of a first image, a second array across the second sub-regions, defining in each a corresponding portion of a second image; wherein each sub-region has a respective average inclination and the average inclinations of the first sub-regions are such that the first image is displayed at least at a first viewing angle and those of the second sub-regions are such that the second image is displayed at least at a second viewing angle different from the first and the second image is substantially not or only partially displayed at least at the first angle. Also, a method of manufacturing the security element.