UV-Fluorescent Varnish Authentication for Covert Security Marks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for applying invisible security marks on packaging materials face issues due to interference from UV curable overprint varnishes containing optical brighteners, which can make the marks visible to the unaided eye and pose hardware problems like inkjet nozzle clogging, especially on non-optically brightened carton stock.
Innovation Solution
Printing with UV-absorbent ink on carton stock without optical brighteners, followed by a UV curable varnish that fluoresces under UV illumination, allowing the security mark to be visible only under UV light, and optionally using a transparent UV fluorescent sheet for enhanced security, enabling uniform gloss and robust authentication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a UV curable overprint varnish containing optical brighteners is applied to protect the packaging surface, then the durability and scuff resistance of the surface is improved, but the UV fluorescence of the security marks is interfered with and the marks become visible to the unaided eye
Solution Approach 1:
The patent removes optical brighteners from the overprint varnish formulation, extracting the harmful component that causes unwanted fluorescence. This allows the varnish to provide protective functions without interfering with the UV-absorbing security marks, resolving the contradiction between surface durability and mark covertness.
Solution Approach 2:
The patent applies different properties to different parts of the packaging system: the overprint varnish is formulated without optical brighteners to maintain covertness in mark areas, while still providing protective functions. The UV-absorbing ink creates localized dark areas that selectively block UV light, creating a contrast pattern that is only visible under UV illumination.
2Ease of manufacture
If UV-absorbent ink is printed on carton stock with optical brighteners, then the security mark can be created, but the mark becomes visible to the unaided eye due to gloss differential and optical brightener interference
Solution Approach 1:
The patent converts the UV-absorbing property of the ink, which initially seemed to cause problems, into the core security mechanism. By using UV-absorbing ink on UV-fluorescing paper (or with a UV-fluorescing overcoat), the ink creates dark areas that block UV light, making the marks visible only under UV illumination rather than to the unaided eye.
3Extent of automation
If digitally printing radiation curable varnish is used to apply security marks, then the marking process can be automated, but hardware problems such as inkjet nozzle clogging occur due to high viscosity and cross-linking
Solution Approach 1:
The patent extracts the security marking function from the overprint varnish application process. Instead of using the varnish itself as the marking medium (which causes clogging), the system uses a separate UV-absorbing ink layer for marking, while the varnish provides only protective functions. This separation eliminates the clogging problem while maintaining automation.
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 ensures a covert and durable security mark that is difficult to remove and replicates, maintaining uniform gloss and visibility only under UV light, enhancing security and authentication efficiency.
Implementation Method 1
information (e.g. text, logos, numbers, or barcodes) is printed using a UV-absorbent ink onto the substrate
Implementation Method 2
a UV curable varnish that fluoresces under UV illumination is applied
Data Source
AI summary
A system of authenticating an item with a security mark includes a substrate (100); wherein the security mark is printed on the substrate with invisible ultraviolet (UV) absorbing ink (102); a coating comprised of UV fluorescent varnish (104) applied over the security mark and substrate; wherein an area comprising the security mark and coating with is illuminated with UV light; wherein a reduced fluorescence image of the security mark is identified; wherein the reduced fluorescence image is compared with the security mark; and wherein the item is authenticated if the reduced fluorescence image matches the security mark.