Banknote Security via Spectral Ink Contrast
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Solution Overview
Problem
Existing security features in valuable documents, such as banknotes, can be recognized by counterfeiters through irradiation with different wavelengths, and require verification under varying lighting conditions, which may not provide sufficient protection against digital copying and forgery.
Innovation Solution
A method utilizing a flat printing area with multiple individual printing areas, each printed with slightly different black inks that appear homogeneous to the naked eye but have a small color difference (Delta E 0.2-1.0) that is detectable only through spectral analysis, using a spectrometer or spectrodensitometer to verify authenticity by comparing measured color distances with a secret master template.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metameric color formulations are used for printing security features, then the security features become visible under different lighting conditions (UV, IR), but this makes them recognizable by counterfeiters through irradiation with different wavelengths
Solution Approach 1:
The patent changes the parameter of color formulation from metameric colors (visible under different wavelengths) to achromatic black inks with extremely small color differences (Delta E 0.2-1.0). This parameter change eliminates the vulnerability to wavelength-based detection while maintaining security through spectral analysis of subtle color variations that are imperceptible to the human eye.
2Productivity
If digital printing processes are used for security documents, then production cost and efficiency improve, but the security features become more susceptible to digital copying and forgery
Solution Approach 1:
The patent applies local quality by printing different black inks with specific Delta E color differences in specific local areas (individual printing areas within a flat printing area). This creates localized spectral characteristics that are imperceptible visually but detectable through spectral analysis, making digital copying difficult while maintaining digital printing efficiency.
3Ease of operation
If traditional security features are used that are visible under different wavelengths, then verification can be performed with simple tools, but the features can be easily detected and copied by counterfeiters
Solution Approach 1:
The patent replaces the mechanical/optical system of wavelength-based detection (UV, IR irradiation) with spectral analysis of color differences. Instead of using different wavelengths to reveal security features, the system uses a spectrometer or spectrodensitometer to measure and compare the spectral characteristics of black inks with Delta E 0.2-1.0 differences, providing verification without requiring special irradiation equipment.
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 method provides enhanced security against forgery by making it difficult for digital copiers to reproduce the color difference and ensures the authenticity can be accurately verified without requiring irradiation with different wavelengths, thereby increasing resistance to counterfeiting.
Implementation Method 1
have a small color difference (Delta E 0.2-1.0) that is detectable only through spectral analysis, using a spectrometer or spectrodensitometer
Data Source
Figure 1~4
AI summary
The invention relates to a method for verifying the authenticity of a security document (10), in particular a banknote (10), wherein the security document (10) has a security document substrate (11) with a planar printing area (20) and the planar printing area (20) has at least two individual printing areas (20.1, ... 20.n), characterized in that the first individual printing area (20.1) is printed with a first black printing ink (30.1) and the second individual printing area (20.2) is printed with a second black printing ink (30.2) and the color difference Delta E30.1-30.2 of the two printing inks (30.1, 30.2) is between 0.2 and 1.0 and the verification of authenticity is carried out by detecting the small difference of the color difference Delta E30.1-30.2 of the two printing inks (30.1, 30.2).