Thin-Film Element With Absorber Layers For Security Documents
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Solution Overview
Problem
Current security elements for data carriers, such as value documents, lack a high counterfeit security feature that provides an attractive visual appearance and angle-dependent optical effects, making them susceptible to unauthorized reproduction.
Innovation Solution
A thin-film element with two absorber layers made from materials with a complex refractive index where the real and imaginary parts differ significantly, combined with a dielectric spacing layer, creating a color-shift effect when viewed from different angles, and integrated into a see-through security element or data carrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional absorber layers with similar real and imaginary refractive index parts are used, then the manufacturing is easier and adhesion is better, but the visual appearance is less attractive and counterfeit security is reduced
Solution Approach 1:
The patent changes the optical parameters of the absorber layers by selecting materials where the real part n and imaginary part k of the complex refractive index differ by at least a factor of 5. This parameter change creates the desired color-shift effect and improves counterfeit security while maintaining manufacturing feasibility through the use of conventional deposition techniques.
Solution Approach 2:
The patent employs composite material structures with specific absorber layers made from materials having distinct real and imaginary refractive index parts, combined with dielectric spacing layers. This composite approach enables both the attractive visual appearance with high counterfeit security and reasonable manufacturing ease by using established thin-film deposition processes.
2Illumination intensity
If absorber layers with large difference between real and imaginary refractive index parts are used, then the color-shift effect and visual appearance are improved, but the layer adhesion may be compromised
Solution Approach 1:
The patent optimizes the optical parameters of absorber layer materials by selecting substances where the real part n and imaginary part k differ by at least a factor of 5. This parameter selection achieves vibrant color-shift effects and superior visual appearance while maintaining acceptable layer adhesion through controlled deposition processes.
3Reliability
If the thin-film element displays strong color-shift effects, then counterfeit security is enhanced, but the complexity of the layer structure increases
Solution Approach 1:
The patent achieves strong color-shift effects and high counterfeit security by changing the optical parameters of absorber layers (selecting materials where real part n and imaginary part k differ by at least a factor of 5) rather than increasing structural complexity. This approach maintains relatively simple layer structures while delivering the desired security performance.
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 thin-film element exhibits a vibrant, angle-dependent color change, providing high counterfeit security and a striking visual appearance, while maintaining a color-neutral appearance in reflected light, enhancing authenticity verification.
Implementation Method 1
thin-film element having an interference layer structure
Implementation Method 2
complex refractive index N=n+ik whose real part n and imaginary part k differ
Data Source
AI summary
The present invention relates to a thin-film element (30) having an interference layer structure for security papers, value documents and the like, having at least two semitransparent absorber layers (34, 38) and at least one dielectric spacing layer (36) arranged between the at least two absorber layers. According to the present invention, it is provided that the two absorber layers (34, 38) are each formed from a material having a complex refractive index N whose real part n and imaginary part k differ at least in a portion of the visible spectral range by a factor of 5 or more.