Fluorescent Inkjet Ink for Security Document Detection
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Solution Overview
Problem
Current inkjet printing technologies face challenges in producing aqueous colored pigment-based inks that achieve high optical density and resistance to smearing or removal from non-UV fluorescing substrates, especially for creating dense black images that exhibit strong visible fluorescence under UV illumination, while being compatible with both drop-on-demand (DOD) and continuous inkjet (CIJ) systems.
Innovation Solution
Development of aqueous colored pigment-based inks, particularly black inks, that incorporate a non-polymeric fluorophore and pigment colorants, with a weight ratio of 70:1 to 0.5:1, which emit fluorescence in the 400-750 nm range when excited by radiation between 200-400 nm, ensuring high rub resistance and visibility under UV light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aqueous pigment-based inks are used to achieve high optical density and resistance to smearing, then image durability and density are improved, but fluorescence visibility under UV light deteriorates
Solution Approach 1:
The patent combines pigment-based inks with fluorescent additives to create a composite ink formulation. The pigment provides optical density and smearing resistance, while the fluorescent additive emits visible light under UV illumination, resolving the contradiction between durability and fluorescence visibility.
Solution Approach 2:
The patent modifies the chemical composition parameters of the ink by incorporating specific fluorescent compounds at controlled concentrations. This parameter change enables the ink to simultaneously achieve high optical density and strong fluorescence emission under UV light.
2Illumination intensity
If fluorescent additives are added to aqueous pigment-based inks to enhance visibility under UV light, then fluorescence emission is improved, but image optical density and rub resistance deteriorate
Solution Approach 1:
The patent optimizes the concentration parameters of fluorescent additives within specific ranges to maximize fluorescence emission while minimizing negative impacts on rub resistance and optical density. By carefully controlling these parameters, the ink achieves balanced performance.
Solution Approach 2:
The patent applies fluorescent additives locally within the ink formulation rather than uniformly throughout all components. This localized approach allows the fluorescent substance to be present where needed for visibility while maintaining the integrity and rub resistance properties of the pigment-based ink system.
3Productivity
If conventional inkjet printing methods are used to print variable data on security documents, then printing speed and efficiency are improved, but image security and resistance to detection deteriorate
Solution Approach 1:
The patent utilizes fluorescent color properties that change under UV illumination to create security features that are invisible or difficult to detect under normal lighting conditions. This color change property enhances image security while maintaining compatibility with conventional inkjet printing methods.
Solution Approach 2:
The patent employs composite ink formulations combining pigments and fluorescent additives that provide both printability and security features. This composite approach enables conventional inkjet printers to produce images with enhanced security characteristics that are difficult to detect and measure.
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 provides highly resistant, high-density, and visibly fluorescent images on non-UV fluorescing substrates, suitable for security documents and other applications, with improved optical density and wet rub resistance.
Implementation Method 1
a non-polymeric fluorophore that when excited by fluorescence-exciting radiation having a peak of at least 200 nm and up to and including 400 nm, exhibits an emission peak of at least 400 nm and up to and including 750 nm
Data Source
AI summary
A fluorescent colored image can be detected in an image on an article. This fluorescent colored image is obtained from applying an aqueous colored pigment-based ink that is capable of fluorescence, onto a suitable non-UV fluorescent substrate. This aqueous colored pigment-based ink has 1-7 weight % of a pigment colorant; and 0.1-2 weight % of a non-polymeric fluorophore that when excited by fluorescence-exciting radiation having a peak of at least 200 nm and up to and including 400 nm, exhibits an emission peak of at least 400 nm and up to and including 750 nm. This aqueous colored pigment-based ink that is capable of fluorescence can be applied using inkjet printing, onto non-UV fluorescent substrates to provide images that can be detected when excited as noted above, which images can be provided on articles such as security documents, currency, and lottery tickets.