Luminescent Material Mixture for Banknote Authentication
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Solution Overview
Problem
Current security features using quasi-resonant luminescent materials for authentication, such as those on banknotes, are becoming less reliable due to their ubiquity and complexity, making it difficult to differentiate between genuine and counterfeit items using exponential decay characteristics.
Innovation Solution
Intermingling at least two luminescent materials with different exponential decay characteristics and mixing them in specific ratios to create a combined emission with a single multi-exponential decay characteristic, allowing for decoding of the individual materials and their ratios through measurement and processing, thereby authenticating the security feature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If quasi-resonant luminescent materials are used for authentication, then authentication capability is provided, but reliability decreases due to ubiquity and complexity
Solution Approach 1:
The patent applies composite materials by intermingling multiple luminescent materials with different exponential decay characteristics within a single security feature. This creates a complex emission profile that is difficult to replicate, thereby improving authentication reliability while managing the complexity through material composition rather than structural complexity
Solution Approach 2:
The patent utilizes parameter changes by varying the decay constants and emission wavelengths of different luminescent materials in the mixture. By controlling these parameters, the security feature produces a distinctive multi-exponential decay signature that enhances reliability without requiring overly complex structural designs
2Measurement precision
If multiple luminescent materials with different decay characteristics are intermingled, then authentication accuracy is improved, but measurement and detection difficulty increases
Solution Approach 1:
The patent applies segmentation by resolving the combined emission into distinct exponential decay components through mathematical analysis. The measurement system detects the overall emission profile and segments it into individual material contributions based on their characteristic decay constants, enabling accurate identification of multiple materials without requiring separate detection for each
Solution Approach 2:
The patent uses an intermediary approach by employing signal processing algorithms as a mediator between the complex multi-material emission and the detection system. The algorithms process the combined decay signal and extract individual material characteristics, simplifying the measurement process while maintaining high accuracy
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 enhances authentication reliability by disguising sophisticated signatures as less complex ones, allowing for accurate differentiation and validation of security features using sensitive detection equipment and signal processing algorithms.
Implementation Method 1
the intensity y of time resolved emissions from quasi-resonant materials, which emit light having a similar wavelength to the excitation source, tend to be dominated by an exponential function of time (t)
Data Source
AI summary
At least two luminescent materials are intermingled within a security feature. The materials are selected from among a larger set of luminescent materials each having a different individual exponential decay characteristic (decay constant and initial amplitude response to the degree of excitation) for photo-luminescent emission from the respective material following excitation. The ratio of the decay constants for any two materials is greater than or equal to about 1.5. The selected materials are mixed in one of a plurality of predetermined ratios. The combined emissions from the intermingled materials appear, to an unsophisticated measuring device, to have a single exponential decay constant. Based on measurements for the decay of the combined emissions following excitation, estimates of the individual decay constants and associated initial emission amplitudes allow decoding of the particular combination of materials and/or their ratios to validate the security feature, authenticating the article.