Reversible Mechano-Luminescent Compound for Security Document Authentication
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Solution Overview
Problem
Existing security documents face challenges in authentication due to the ease of counterfeiting facilitated by the widespread use of luminescent inks in non-fiduciary sectors, and compounds exhibiting mechanofluorochromism and thermofluorochromism properties are not suitable for use in security inks or varnishes as they lose properties when heated to their melting point, reacting with the document material.
Innovation Solution
A method utilizing a reversible mechano-luminescent compound that changes fluorescence color when subjected to UV radiation and heat without mechanical stress, allowing verification of authenticity by heating the document to a temperature below its melting point, inducing a color change from a first to a second fluorescent color.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If compounds exhibiting mechanofluorochromism and thermofluorochromism are used in security inks or varnishes, then the security document can respond to multiple stimuli, but the compound loses its properties when heated to its melting point and reacts with the document material
Solution Approach 1:
The patent modifies the molecular structure of the compound by introducing specific substituents (R groups) that lower the melting point and stabilize the compound at operating temperatures. This structural parameter change allows the compound to maintain its mechanofluorochromic and thermofluorochromic properties without degrading or reacting with the document material when heated.
Solution Approach 2:
The patent formulates the compound within a specific matrix or carrier system that provides thermal stability and prevents direct contact between the compound and the document substrate. This composite approach allows the compound to exhibit its multi-stimuli response while being protected from degradation and unwanted reactions.
2Ease of manufacture
If the surface of the support is heated to a temperature equivalent to or higher than the melting point of the compound, then the compound can be reprocessed, but it passes into the liquid phase and reacts with the support material
Solution Approach 1:
The patent carefully controls the heating parameters (temperature and duration) to remain below the compound's melting point during normal operation, while still achieving the desired thermofluorochromic effect. This parameter optimization allows the compound to respond to thermal stimuli without degrading or reacting with the support material.
3Ease of operation
If luminescent inks are widely distributed in non-fiduciary sectors, then these inks become easily accessible, but their supply via unsecured channels facilitates counterfeiting
Solution Approach 1:
The patent creates a security feature with unique local properties - a compound that responds to both mechanical stress and thermal stimulation in a specific sequence, producing distinct color changes. This localized multi-stimuli response creates an authentication mechanism that is difficult to replicate with conventional single-stimuli luminescent inks, even if those inks are easily accessible.
Solution Approach 2:
The patent implements a dynamic authentication system where the security feature can change its optical properties in response to different stimuli (mechanical then thermal). This dynamic, multi-stage response creates a complex authentication pattern that is much harder to counterfeit than static luminescent features, while still using compounds that can be applied to various document types.
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
This method enhances authentication by ensuring the compound's properties are maintained within the document, preventing reaction with the material and providing a reliable means for the public and banks to verify authenticity using UV lamps and heat sources.
Implementation Method 1
a zone (4) with, within it or on the surface of this zone, a reversible mechano-luminescent compound... subjected to ultraviolet radiation so that the whole of said zone is visible to the naked eye under a first fluorescent color
Implementation Method 2
a step which consists of heating at least said zone to a temperature of at least 50°C, without subjecting it to the slightest friction or mechanical stress, revealing the authenticity said document being confirmed by the change from said first color to a second fluorescent color, different from the first
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention concerns a method for checking the authenticity of a security document, in particularly a fiduciary document, which comprises an area with, within or at the surface of this area, a reversible mecanoluminescent compound of formula (i): In which R represents an alkyl chain comprising 1 to 12 carbon atoms, which comprises a step in which said area is subjected to ultraviolet radiation such that the whole of said area is visible to the naked eye in a first fluorescent colour (C1), characterised by the fact that it also comprises a step that consists of heating at least said area to a temperature of at least 50° C, without subjecting it to any friction or mechanical stress whatsoever, the revealing of the authenticity of said document being confirmed by the shift from said first colour (C1) to a second fluorescent colour (C2) different from the first.