UV-Vis Curable Security Inks with Silver Nanoplatelets
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Solution Overview
Problem
Existing security inks for producing dichroic security features on value documents suffer from limited mechanical resistance and high production costs, making them unsuitable for industrial production at high speeds.
Innovation Solution
Development of UV-Vis radiation curable security inks containing silver nanoplatelets with specific size and surface stabilizing agents, combined with a cycloaliphatic epoxide and cationic photoinitiators, to achieve improved mechanical resistance and attractive visual appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high concentrations of silver platelets are used in UV radically curable inks, then dichroic security features with attractive visual appearance are obtained, but mechanical resistance is impaired and production cost increases
Solution Approach 1:
The patent changes the concentration parameter of silver platelets from high (3:1.1 weight ratio) to optimized levels, and modifies the binder type from UV radically curable to UV-curable formulations with specific additives. This parameter optimization maintains the dichroic visual effect while improving mechanical resistance and reducing production costs.
Solution Approach 2:
The patent uses composite material formulation combining silver platelets with specifically selected UV-curable binders and additives (such as polyols, isocyanates, or other curing agents). This composite approach allows optimization of both optical properties and mechanical strength, resolving the contradiction between visual appearance and mechanical resistance.
2Speed
If UV radically curable inks are used to produce dichroic security features, then fast curing is achieved, but mechanical resistance of the security element is limited
Solution Approach 1:
The patent modifies the curing mechanism parameter by switching from radical curing to cationic curing or hybrid curing systems. This parameter change maintains fast curing capability while producing coatings with superior mechanical resistance, as cationic curing systems generally provide better crosslink density and mechanical properties.
3Ease of operation
If solvent-based inks are used for dichroic security features, then good flow and coverage are achieved, but additional air drying step is required and mechanical resistance is limited
Solution Approach 1:
The patent extracts and eliminates the air drying step from the production process by using water-free or low-VOC ink formulations that cure directly upon UV exposure. This removes the intermediate drying step while maintaining good flow and coverage properties through optimized ink rheology and composition.
4Productivity
If high printing speeds are required for industrial production, then productivity is improved, but the complexity of ensuring quality security features increases
Solution Approach 1:
The patent replaces complex multi-step production processes with a single UV-curing step that can be integrated directly into high-speed printing lines. The UV-curable formulation allows for immediate curing upon application, eliminating the need for separate drying or processing steps, thus enabling high-speed industrial production while maintaining quality consistency.
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 new security inks enable the production of dichroic security features with enhanced mechanical resistance and attractive visual appearance, suitable for high-speed industrial printing of value documents.
Implementation Method 1
UV-Vis radiation curable security inks for producing dichroic security features
Implementation Method 2
dichroic security features exhibiting a first color upon viewing in transmitted light and a second color different from the first color upon viewing in incident light
Data Source
AI summary
The present invention provides a UV-Vis radiation curable security ink for producing a security feature for securing value documents, wherein said security feature exhibits a blue color upon viewing in transmitted light and a metallic yellow color upon viewing in incident light. The UV-Vis radiation curable security ink comprises a cationically curable or a hybrid curable ink vehicle, and silver nanoplatelets bearing a surface stabilizing agent of general formula (I)whereinthe residue RA is a C2-C4alkyl group substituted with a hydroxy group;the residue RB is selected from a C1-C4alkyl group, and a C2-C4alkyl group substituted with a hydroxy group; and Cat+ is an ammonium cation of general formula +NH2RCRD, wherein the residue RC is a C2-C4alkyl group substituted with a hydroxy group; and the residue RD is selected from a C1-C4alkyl group, and a C2-C4alkyl group substituted with a hydroxy group.