Tailored Luminescent Substances for Value Document Security
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Solution Overview
Problem
The limited number of luminescent substances suitable for authenticity features in value documents and security papers due to uncharacteristic, wide spectra and insufficient emission intensity restricts their identification and practical use, especially for automatic authenticity recognition.
Innovation Solution
Development of luminescent substances with tailored excitation and emission spectra in the visible or infrared range, specifically using compounds with rare earth elements and specific stoichiometric ratios, allowing for altered excitation and emission properties and enabling narrowband luminescence for enhanced selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional luminescent substances are used for authenticity features, then the substances are readily available and easy to implement, but the substances have uncharacteristic wide spectra and insufficient emission intensity that restrict identification and simultaneous use of multiple substances
Solution Approach 1:
The patent applies parameter changes by systematically varying the composition parameters of luminescent substances, specifically using different rare earth metal dopants (Eu, Tb, Dy, Er, Yb, Pr, Nd) in controlled concentrations within host lattices. This enables precise tuning of emission spectra to achieve narrowband luminescence with distinct spectral fingerprints, resolving the contradiction between material availability and spectral characterization precision
Solution Approach 2:
The patent employs composite materials by combining rare earth metal dopants with specific host lattice structures (such as silicates, phosphates, and oxides). These composite structures provide well-defined crystal field environments that narrow the emission spectra while maintaining high emission intensity, thereby enabling multiple substances to be used simultaneously with distinct spectral characteristics
2Ease of operation
If luminescent substances with visible emission are used, then the substances can be detected by the eye for authenticity testing, but special detectors are required when emission is outside the visible spectral range
Solution Approach 1:
The patent applies local quality by designing luminescent substances with emission spectra specifically tailored to particular detection needs. Some substances are optimized for visible range emission to enable simple visual or UV-based authenticity testing, while others are designed for infrared or ultraviolet emission when enhanced security requiring special detectors is needed. This localized optimization of spectral properties allows flexibility in detection method selection
3Adaptability or versatility
If multiple luminescent substances are used simultaneously for enhanced security, then the authenticity features become more diverse, but the uncharacteristic wide spectra of conventional substances make identification and simultaneous use impracticable
Solution Approach 1:
The patent applies segmentation by dividing the luminescent material system into multiple distinct substances, each with a specific rare earth metal dopant and host lattice combination that produces a unique spectral signature. This segmentation creates well-separated emission bands that can be individually identified, enabling multiple substances to be used simultaneously in authenticity features without spectral overlap confusion
Solution Approach 2:
The patent uses parameter changes to systematically differentiate multiple luminescent substances by varying dopant concentration, host lattice composition, and crystal structure parameters. These controlled parameter variations produce distinct emission intensities, wavelengths, and spectral shapes for each substance, enabling reliable identification and simultaneous use in multi-layered authenticity verification systems
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 tailored luminescent substances provide a broader range of authenticity features, enabling more effective identification and increased security through varied excitation and emission spectra, and allow for multiple substances to be used simultaneously, enhancing the security and authenticity verification of value documents.
Implementation Method 1
at least one luminescent substance is used for protection. Preferably, its emission spectrum is in the visible or infrared spectral range (VIS, IR)
Implementation Method 2
the emission band can follow the Stokes or anti-Stokes rule or quasi-resonance can be observed
Implementation Method 3
the emission band can follow the Stokes or anti-Stokes rule or quasi-resonance can be observed
Implementation Method 4
the emission band can follow the Stokes or anti-Stokes rule or quasi-resonance can be observed
Data Source
AI summary
The invention relates to a printed value document having at least one luminescent substance.