Printed Security Feature Using Dual-Ink UV Fluorescence
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Solution Overview
Problem
Current printed security features are not sufficiently difficult to counterfeit and lack advanced features that require high-precision printing, making them vulnerable to forgery.
Innovation Solution
A printed security feature with geometric elements printed using two inks that exhibit the same appearance under visible light but produce distinct optical responses under non-visible light, requiring precise registration to conceal and reveal a two-dimensional graphic element, thereby enhancing security and authenticity verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple inks with different optical properties are used to create concealed graphic elements, then the security feature becomes more difficult to counterfeit, but the printing process complexity increases
Solution Approach 1:
The printed area is divided into multiple printed portions (first, second, and third portions) with different ink configurations. The first and second portions contain geometric elements printed with single inks, while the third portion contains geometric elements printed with multiple inks. This segmentation allows the security feature to exhibit different optical responses in different regions, creating concealed graphic elements that require precise multi-ink printing while maintaining overall process feasibility.
Solution Approach 2:
Different regions of the printed area are assigned different ink properties and configurations. The first printed portion uses first ink with specific optical properties, the second printed portion uses second ink with different optical properties, and the third printed portion uses both inks to create the concealed graphic element. This local differentiation enables the security feature to provide both visible design elements and concealed verification elements within a single printing process.
2Reliability
If high-precision registration is required to conceal boundaries under visible light, then the security feature becomes more secure, but the manufacturing difficulty increases
Solution Approach 1:
The printing process is designed to preemptively address registration challenges by using inks with complementary optical properties. The first and second inks are formulated to be substantially invisible when printed in registration, so that any minor registration errors do not reveal visible boundaries. This preliminary anti-action compensates for potential manufacturing imprecision while maintaining security.
Solution Approach 2:
The optical parameters of the inks are specifically selected and adjusted so that the first and second inks are substantially invisible when combined in registration. By changing the optical properties (absorption, reflection, fluorescence) of the inks rather than relying solely on perfect registration, the system achieves both high security and manufacturing feasibility.
3Ease of operation
If inks with identical visible appearance but different non-visible light responses are used, then authentication is simplified, but the ink formulation complexity increases
Solution Approach 1:
The first and second inks are designed to exhibit substantially the same optical appearance (color, brightness, transparency) under visible light, making them indistinguishable to the human eye. However, they have different optical responses when illuminated with non-visible light (such as ultraviolet light), allowing authentication using simple UV illumination without requiring complex analysis equipment.
Solution Approach 2:
The authentication mechanism replaces complex optical analysis with simple UV illumination. Instead of requiring sophisticated instruments to detect ink differences, the system uses non-visible light excitation to produce easily observable optical responses (fluorescence, phosphorescence, or other light interactions) that can be detected with simple UV lamps, greatly simplifying the authentication process.
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 significantly increases the difficulty of counterfeiting and ensures that only high-precision printing can produce the feature, making it harder for counterfeiters to replicate, while allowing simple tools like UV light to verify authenticity.
Implementation Method 1
at least the first ink being an ink which responds to non-visible light excitation by producing a characteristic optical response differentiating the first ink from the second ink
Data Source
AI summary
There is described a printed security feature (10) provided onto a printable substrate, which printed security feature includes a printed area (11) with at least a first printed section consisting of a multiplicity of geometric elements (GE, 15) printed with a given distribution over the printed area. The geometric elements are printed with at least first and second inks which exhibit the same or substantially the same optical appearance when illuminated with visible white light, such that the printed security feature produces a first graphical representation (A1) when illuminated with visible white light. At least the first ink is an ink which responds to non-visible light excitation by producing a characteristic optical response differentiating the first ink from the second ink. The printed security feature produces a second graphical representation (B1) when illuminated with non-visible light, which exhibits a distinctive two-dimensional graphic element (B) which is revealed only when the printed security feature is illuminated with non-visible light. The first printed section is subdivided into at least first and second printed portions (P1, P2), adjacent to the distinctive two-dimensional graphic element, and a third printed portion (P3), inside boundaries (200) of the distinctive two-dimensional graphic element. In the first, respectively second printed portion, the geometric elements are printed with the first, respectively second ink. In the third printed portion, the geometric elements are sub-divided into first and second contiguous portions (GE_a, GE_b) which are respectively printed with the first and second inks. The first and second inks are printed in register one with respect to the other so that the boundaries of the distinctive two-dimensional graphic element are not visible when the printed security feature is illuminated with visible white light and the distinctive two-dimensional graphic element only becomes visible when the printed security feature is illuminated with non-visible light.