Oxidative Drying Intaglio Ink for Low Set-Off Security Printing
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Solution Overview
Problem
Oxidative drying intaglio inks used in intaglio printing processes suffer from set-off issues, where ink transfers from one printed sheet to another, especially in high-quality security documents, necessitating improved drying performance and set-off characteristics.
Innovation Solution
The use of oxidative drying intaglio inks comprising polythiol compounds, fusible waxes, and driers, along with a specific wiping process using a polymeric wiping cylinder and alkaline aqueous solution, followed by air drying, to form security features on substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxidative drying intaglio inks are used for high-quality security document printing, then fine tapering lines and design quality are improved, but set-off problems worsen due to pronounced relief of intaglio printed patterns
Solution Approach 1:
The patent modifies the chemical composition parameters of the oxidative drying ink by incorporating specific compounds (polythiols, fusible waxes, and metal driers) in optimized proportions. This changes the drying kinetics and film formation characteristics, allowing the ink to set faster and reduce set-off while maintaining the intaglio relief quality necessary for fine tapering lines.
Solution Approach 2:
The patent creates a composite ink formulation combining multiple functional components: oxidative drying agents for rapid setting, polythiols for adhesion and film formation, fusible waxes for controlled drying and relief enhancement, and metal driers as catalysts. This composite material approach resolves the contradiction by integrating properties that simultaneously enable fine line quality and reduce set-off.
2Reliability
If ink layer thickness is increased for sufficient material detection and sensing, then security feature detectability is improved, but set-off problems worsen due to excess ink transfer
Solution Approach 1:
The patent changes the rheological and drying parameters of the ink formulation to enable thicker deposits without increasing set-off. The optimized composition controls viscosity, drying rate, and film formation kinetics, allowing sufficient material thickness for detection while preventing excessive ink transfer to subsequent sheets.
Solution Approach 2:
The patent employs preliminary action by incorporating fusible waxes and optimizing drier content to accelerate initial film formation and setting. This preliminary stabilization of the ink layer prevents set-off even when thicker deposits are applied for enhanced detection and sensing capabilities.
3Productivity
If driers are added to accelerate oxidative drying process, then drying speed is improved, but ink formulation complexity increases
Solution Approach 1:
The patent optimizes the concentration and type of metal driers in the ink formulation to achieve accelerated drying speeds. By carefully controlling the drier content within specific ranges and combining it with polythiols and fusible waxes, the formulation achieves fast drying without excessive complexity, balancing productivity with formulation manageability.
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 effectively reduces set-off issues, ensuring high-quality, durable security features on value documents by enhancing drying performance and adhesion to the substrate.
Implementation Method 1
Oxidative drying inks are commonly used for intaglio printing processes. Said inks 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.
Implementation Method 2
iv) one or more fusible waxes present in a total amount from about 1 wt-% to about 10 wt-%
Implementation Method 3
one or more polythiol compounds present in a total amount larger than 0.5 wt-%
Data Source
AI summary
The present invention relates to the field of processes for producing a security feature on a substrate by an intaglio printing process comprising a step a) of inking an intaglio engraved printing plate with an oxidative drying intaglio ink, said intaglio engraved printing plate being at a printing plate temperature between about 45° C. and about 85° C.; a step b) of wiping off any excess the oxidative drying intaglio ink using a paper of a tissue wiping system or using a polymeric wiping cylinder and cleaning said polymeric wiping cylinder with an alkaline aqueous wiping solution in combination with one or more mechanical means; a step c) of transferring said oxidative drying intaglio ink in the form of the security feature on the substrate; and a step d) of drying the oxidative drying intaglio ink in the presence of air so as to form the security feature.