Directional Metal Coating for Plasmonic Security Elements
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Solution Overview
Problem
Current methods lack efficient processes for integrating plasmonic nanostructures into security devices, particularly due to challenges in metallizing these structures without affecting other areas of the security element, which hinders their effective use in preventing counterfeiting and ensuring authenticity.
Innovation Solution
A method involving a dielectric substrate with an array of plasmonic nanostructure elements and reduced-metallising relief elements, where the substrate is directionally coated with a metal layer to ensure thicker coating on raised portions and thinner, potentially transparent coating on inclined portions, allowing for precise metallization of plasmonic regions while minimizing reflective interference from non-plasmonic areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal layer is applied to the substrate to metallize the plasmonic nanostructure areas, then the plasmonic nanostructures can be formed, but the inclined portions (non-plasmonic areas) also receive metal coating which creates reflective interference
Solution Approach 1:
The patent applies directional coating at a specific angle of incidence (45 degrees) to create non-uniform metal layer thickness across the substrate surface. The inclined portions receive thinner metal coating compared to the raised plasmonic nanostructure areas, thereby reducing reflective interference from non-plasmonic regions while maintaining plasmonic functionality where needed.
2Ease of manufacture
If conventional printing techniques are used to create security elements, then the manufacturing process is simple, but the security elements can be easily replicated and do not provide sufficient anti-counterfeiting protection
Solution Approach 1:
The patent replaces conventional mechanical printing processes with a directional coating process that deposits metal layers at specific angles to create plasmonic nanostructures. This substitution enables the formation of optically active structures with controlled metal thickness distribution, providing anti-counterfeiting capabilities through plasmonic effects that cannot be replicated by standard printing techniques.
3Manufacturing precision
If the metal layer thickness is increased to ensure complete coverage, then all areas are sufficiently metallized, but the inclined portions become overly reflective and interfere with optical effects
Solution Approach 1:
The patent introduces the dimension of coating angle by applying the metal layer at 45 degrees incidence rather than perpendicular deposition. This angular approach creates natural thickness variation across the substrate surface, with thinner coating on inclined portions and thicker coating on raised portions, thereby controlling reflectivity without requiring complex thickness control mechanisms.
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
This approach enables the creation of security device components with functioning plasmonic nanostructures that remain visually striking while being integrated seamlessly into security documents, enhancing authenticity verification and resistance to counterfeiting by maintaining the optical effects and high-resolution imagery capabilities of plasmonic nanostructures.
Implementation Method 1
directionally coating the first surface of the substrate with a metal layer
Implementation Method 2
Plasmonic nanostructures are structures that generate colour from the resonant interactions between light and metallic nanostructures where collective free-electron oscillations within the metallic nanostructure coupled to electromagnetic fields in a neighbouring dielectric material
Implementation Method 3
the array of reduced-metallising relief elements defining inclined portions of the first surface having an inclination relative to the plane of the substrate
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3A~3B
AI summary
A method of manufacturing a security device component is provided. The method comprises: a) providing a dielectric substrate, the substrate having a first surface defining a relief structure, wherein the relief structure comprises an array of plasmonic nanostructure elements, the array of plasmonic nanostructure elements defining raised portions and recessed portions of the first surface, and an array of reduced-metallising relief elements, the array of reduced-metallising relief elements defining inclined portions of the first surface having an inclination relative to the plane of the substrate greater than the inclination of the raised portions and/or the recessed portions of the first surface; b) directionally coating the first surface of the substrate with a metal layer such that the metal layer coating the raised portions and/or the recessed portions of the of the first surface defined by the array of plasmonic nanostructure elements is thicker than any metal layer coating the inclined portions of the first surface defined by the array of reduced-metallising relief elements, wherein the plasmonic nanostructure elements and the metal layer, in combination, provide an array of functioning plasmonic nanostructures.