Magnetic Oxidative Drying Inks for Security Documents
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Solution Overview
Problem
Existing magnetic machine-readable inks for security documents, particularly those used in intaglio printing, face limitations due to dark optical appearance and stability issues, which restrict color gamut and lead to set-off problems during the printing process.
Innovation Solution
Development of magnetic oxidative drying inks incorporating core-shell pigment particles with a silver external layer and benzotriazole compounds, which provide improved stability and drying performance, allowing for the creation of bright hues and reducing set-off issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If magnetic pigment particles with silver external layer are used, then color brightness is improved, but storage stability deteriorates
Solution Approach 1:
Benzotriazole compounds are introduced as intermediary substances that form protective complexes with silver ions in the magnetic pigment particles. This intermediary layer prevents direct oxidation of the silver external layer while maintaining the bright color appearance, thus resolving the contradiction between color brightness and storage stability
Solution Approach 2:
The chemical environment within the ink formulation is modified by adding benzotriazole compounds, which change the oxidation resistance parameters of the silver external layer. This parameter change allows the ink to maintain both bright color and improved storage stability
2Speed
If oxidative drying varnish is used, then drying speed is improved, but set-off increases
Solution Approach 1:
The ink formulation creates local quality differences through the benzotriazole compounds that modify the drying characteristics specifically in the intaglio printed areas. This localized modification allows fast drying where needed while reducing set-off tendency in the overall printed sheet
Solution Approach 2:
The ink is formulated as a composite material combining oxidative drying varnish with benzotriazole compounds. This composite structure provides both the rapid drying properties of oxidative drying and the set-off reduction benefits of the benzotriazole additive
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 magnetic oxidative drying inks achieve enhanced stability, improved color stability, and reduced set-off, enabling the production of secure, high-quality security documents with improved shelf life and printing performance.
Implementation Method 1
Magnetic inks have been widely used in the field of security documents... to confer the security document an additional covert security feature. Due to their magnetic properties, security features printed with a magnetic ink may be machine authenticated
Implementation Method 2
Oxidative drying inks are commonly used for intaglio printing processes... which dry by oxidation in the presence of oxygen, in particular in the presence of the oxygen of the atmosphere. During the drying process, the oxygen combines with one or more components of the ink vehicle, converting the ink to a semi-solid or a solid state
Data Source
AI summary
The present invention relates to the field of magnetic machine readable oxidative drying suitable for intaglio printing of security documents. In particular, the invention relates to magnetic oxidative drying ink for intaglio printing on a substrate, said magnetic oxidative drying ink having a viscosity in the range of about 3 to about 60 Pa s at 40° C. and 1000 s−1 and comprising a) at least one oxidative drying varnish, b) a plurality of core-shell pigment particles comprising a magnetic core and an external layer made of silver and c) one or more stabilizers selected from benzotriazole compounds.