ZnS Security Feature With Deep-Red Luminescence Verification
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Solution Overview
Problem
Existing zinc sulfide electroluminescent materials do not efficiently luminesce in the deep red spectral range and lack stable, verifiable luminescence properties for secure applications in security documents, requiring high-frequency, high-voltage fields for detection.
Innovation Solution
A zinc sulfide luminophore with both cubic and hexagonal phase portions, doped with copper and other elements, exhibits efficient electroluminescence in the deep red range and thermally or optically stimulated luminescence, allowing for reliable verification through thermally stimulated luminescence (TSL) or optically stimulated luminescence (OSL) without high-voltage electrical fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional zinc sulfide electroluminescent materials are used, then electroluminescence can be achieved, but efficient luminescence in the deep red spectral range is not obtained and stable verifiable luminescence properties are lacking
Solution Approach 1:
The patent applies parameter changes by modifying the crystal phase composition of zinc sulfide luminophores, specifically creating a mixture of cubic and hexagonal phases with controlled ratios. This phase composition parameter change enables simultaneous achievement of deep red electroluminescence efficiency and stable thermally stimulated luminescence properties, resolving the contradiction between illumination intensity and reliability
Solution Approach 2:
The invention uses composite materials by combining zinc sulfide with copper doping and creating a mixed crystal phase structure (cubic and hexagonal phases). This composite approach at the crystallographic level provides both the deep red luminescence efficiency and the stable verification properties through the synergistic effect of different phases and dopants
2Difficulty of detecting and measuring
If high-frequency, high-voltage electrical fields are used for detection, then luminescence can be detected, but the detection process becomes complex and requires specialized equipment
Solution Approach 1:
The patent replaces the electrical field detection method with thermal or optical stimulation methods. Instead of using high-voltage electrical fields to detect luminescence, the invention uses thermally stimulated luminescence (TSL) or optically stimulated luminescence (OSL), which can be detected with simpler thermal or optical equipment while maintaining high verification accuracy
Solution Approach 2:
The invention changes the detection parameter from electrical field stimulation to thermal or optical stimulation. By utilizing the TSL or OSL properties of the zinc sulfide luminophore, the detection process can be performed using temperature control or optical excitation instead of high-voltage electrical fields, reducing detection complexity while preserving measurement precision
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 zinc sulfide luminophore provides stable, verifiable luminescence properties suitable for security documents, enabling reliable authentication through distinct luminescence signals that can be detected using thermal or optical stimulation, enhancing security features' exclusivity and reliability.
Implementation Method 1
The zinc sulfide luminophore emits as an electroluminophore in the deep red spectral range
Implementation Method 2
exhibits further luminescence behavior... reliable verification through thermally stimulated luminescence (TSL)
Implementation Method 3
reliable verification through thermally stimulated luminescence (TSL) or optically stimulated luminescence (OSL)
Data Source
AI summary
A security feature is presented for a security or value document. The security feature comprises a zinc sulfide luminophore in the form of particles. The zinc sulfide luminophore has the general chemical formula ZnS:Cux, My, Xz; here, M represents one or more elements from a group comprising the chemical elements Co, In and Ni; X represents one or more elements from a group comprising the halides F, Cl, Br and I; and the following applies: 0<x<0.002 and 0::; y<0.00015 and 0::; z<0.00050. The particles each have cubic phase portions and hexagonal phase portions. When excited by an electrical field, the zinc sulfide luminophore emits a first radiation in the range of the light spectrum between 580 nm and 780 nm. When excited by heating the luminophore to a temperature between 100° C. and 150° C., the zinc sulfide luminophore emits a second radiation in the light spectrum.