Garnet Optical Storage Phosphor for Authenticity Features
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Solution Overview
Problem
Current optical storage phosphors used for authenticity features are chemically unstable, prone to light instability, and have issues with spectral storage properties, slow luminescence, and low emission intensity, making them difficult to use as quick machine-readable security features.
Innovation Solution
An optical storage phosphor with a garnet structure, specifically composed of Gd3(Al5)O12 with deviations from ideal stoichiometry and co-doping, which adjusts the defect structure to enhance stability, readability, and spectral properties, allowing for targeted modification of storage behavior and luminescence characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical storage phosphors are used for authenticity features, then they can store energy and release luminescence, but they suffer from chemical instability, light instability, slow intrinsic luminescence, and require high energy charging
Solution Approach 1:
The patent changes the fundamental parameters of the phosphor material by using a garnet structure (Gd3Al5O12) doped with cerium and other rare earth elements, which fundamentally alters the chemical stability, luminescence speed, and energy requirements compared to conventional phosphors like SrS:Eu or Sr4Al14O25:Eu,Dy
Solution Approach 2:
The invention creates a composite phosphor material combining multiple elements (Gd, Al, O, Ce, and optionally La, Lu, Y, Ga, Sc, Si, Ge, and other dopants) in a garnet structure, achieving synergistic effects that simultaneously improve chemical stability, reduce luminescence time, and lower charging energy requirements
2Quantity of substance
If conventional optical storage phosphors are used, then they exhibit storage properties, but they show intense persistent luminescence (afterglow) that interferes with rapid machine reading
Solution Approach 1:
The patent optimizes the trap depth and trap center characteristics by carefully selecting dopant concentrations and garnet composition, creating a balance where sufficient charge carriers are stored during charging but can be rapidly extracted during readout, eliminating the problematic afterglow effect
Solution Approach 2:
The invention enables a clear separation between charging and reading phases through controlled luminescence behavior - the phosphor stores charge during charging pulses and then rapidly releases it during reading pulses, creating distinct periodic cycles without overlapping signals
3Use of energy by moving object
If conventional optical storage phosphors are used, then they can be charged with energy, but they require high energy input and have unmatched spectral storage properties
Solution Approach 1:
The patent adjusts the spectral characteristics by selecting specific rare earth element combinations and doping concentrations, which modifies the absorption and emission spectra to achieve both lower charging energy requirements and enhanced spectral discrimination for accurate authentication
Solution Approach 2:
The invention creates specific local electronic environments within the garnet structure through targeted doping, where cerium and other rare earth elements create localized energy levels that facilitate low-energy charging while maintaining distinct spectral signatures for precise measurement
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 a stable, rapidly readable, and highly secure authenticity feature with improved spectral and charging properties, reducing the risk of counterfeiting and enhancing the reliability of authenticity testing.
Implementation Method 1
Substances such as suitably doped alkaline earth sulfides (e.g. SrS:Eu,Sm), halides e.g. BaFBr:Eu), aluminates (e.g. SrAl 2 O 4 ,:Eu,Tm), oxides (e.g. MgO:Tb, BeO), Al2O3:C) and other substances that absorb energy in the form of X-rays, UV, VIS or radioactive radiation, store it and only release it again in the form of luminescence under targeted stimulation.
Implementation Method 2
The luminous centers are stimulated with light. At least some of the excited charge carriers from the luminous centers pass into a conduction band of the OSP, while the remaining charge carriers relax into the ground state of the luminous centers with the emission of photoluminescence.
Implementation Method 3
The charge carriers in the conduction band can diffuse and some of these charge carriers reach trap centers where they are bound.
Implementation Method 4
If light is used as a stimulus, it is called optically stimulated luminescence (OSL).
Data Source
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AI summary
The invention relates to an optical storage phosphor, a method for verifying a security feature, a device for carrying out a method, a security feature, and a security document. In particular, an inorganic optical storage phosphor is specified, comprising a garnet structure and the following composition: (GdxLny)(GamAlnAk)O12±d : Cep Qq Rr Tt, wherein - Ln comprises at least one of the following elements: La, Lu, Y; - A comprises at least one of the following elements: Ge, Sc, Si; - Q comprises at least one of the following elements: Ag, Cr, Hf, Mo, Nb, Sn, Ta, Ti, W, Zr; - R comprises at least one of the following elements: Bi, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb; - T comprises at least one of the following elements: B, F, Li, Mg, K, Na; - 1.0 ≤ x ≤ 3.2 and 0 ≤ y ≤ 1.65 ; - 0.5 ≤ m ≤ 5.2, 0 ≤ n ≤ 4.7 and 0 ≤ k ≤ 0.5, where 4.8 ≤ m + n + k ≤ 5.2; - 0 ≤ p ≤ 0.1, where p = 0 only for Q = Zr; - 0 ≤ q ≤ 0.05; - 0 ≤ r ≤ 0.05; - 0 ≤ t ≤ 0.1; - 0 ≤ d ≤ 0.5; - p + q > 0.002; - q+r > 0.002; and - 2.8 ≤ x+y+p+r ≤ 3.2.