Iron(II) Orthophosphate Security Inks for NIR Authentication
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Solution Overview
Problem
Current security inks for printing machine-readable security features face limitations due to the lack of IR-absorbing materials with high chemical stability, high reflectance in the visible range, and low toxicity, which are also cost-effective and easy to manufacture.
Innovation Solution
Development of security inks using crystal water-free iron(II) orthophosphates, metal orthophosphates, pyrophosphates, and metaphosphates with specific metal compositions, which provide high absorption in the NIR range while maintaining high reflectance in the visible range, and are manufactured using a method involving iron compounds, reduction agents, and metal donors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black is used as IR absorbing material, then strong absorption in the visible domain is achieved, but design freedom is limited due to strong absorption in the visible domain
Solution Approach 1:
The patent changes the material parameter from carbon black to crystal water-free iron(II) orthophosphates, fundamentally altering the absorption characteristics. This new material provides strong NIR absorption while maintaining high visible reflectance, thus resolving the contradiction between IR absorption strength and design freedom.
Solution Approach 2:
The patent employs composite material design by combining crystal water-free iron(II) orthophosphates with specific metal compounds (such as copper, zinc, nickel, cobalt, manganese, calcium, strontium, barium, or aluminum compounds) to create an ink composition that achieves both strong NIR absorption and high visible reflectance, enabling design freedom.
2Reliability
If conventional IR absorbing materials are used, then machine readable security features are provided, but chemical stability is insufficient
Solution Approach 1:
The patent changes the chemical composition parameter by using crystal water-free iron(II) orthophosphates as the base material, which inherently provides superior chemical stability compared to conventional IR absorbing materials while maintaining the required machine readable security feature through strong NIR absorption.
Solution Approach 2:
The patent creates a composite material system combining crystal water-free iron(II) orthophosphates with stable metal compounds, where the composite structure enhances chemical stability while preserving the IR absorbing properties necessary for security features.
3Reliability
If conventional IR absorbing materials are used, then security features are provided, but reflectance in the visible range is insufficient
Solution Approach 1:
The patent changes the optical parameter by selecting crystal water-free iron(II) orthophosphates, which have distinct spectral absorption characteristics that provide strong NIR absorption while maintaining high visible reflectance, thus resolving the contradiction between security feature reliability and visible range reflectance.
Solution Approach 2:
The patent develops a composite ink material combining crystal water-free iron(II) orthophosphates with metal compounds that enhance visible reflectance while maintaining NIR absorption, achieving both security feature reliability and high visible range reflectance simultaneously.
4Reliability
If complex IR absorbing materials are used, then absorption properties are improved, but manufacturing complexity increases
Solution Approach 1:
The patent simplifies the manufacturing process by using crystal water-free iron(II) orthophosphates as the base material, which can be easily combined with common metal compounds through straightforward chemical reactions, reducing manufacturing complexity while maintaining excellent absorption properties.
Solution Approach 2:
The patent employs a composite material approach where crystal water-free iron(II) orthophosphates are combined with readily available metal compounds (copper, zinc, nickel, cobalt, manganese, calcium, strontium, barium, or aluminum compounds), enabling simple and cost-effective manufacturing while achieving superior absorption properties.
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 exhibit high absorption in the NIR range, high reflectance in the visible range, and improved chemical stability, making them suitable for authenticating security documents with enhanced counterfeiting resistance and ease of production.
Implementation Method 1
IR absorbing materials are based on the absorption of electromagnetic radiation due to electronic transitions in a spectral range between 780 nm and 1400 nm (range provided by CIE (Commission Internationale de l'Eclairage)), this part of the electromagnetic spectrum being usually referred to as the NIR-domain
Implementation Method 2
should not absorb in the visible range (400 nm to 700 nm), such as to allow its use in all types of visibly colored inks and also in markings which are invisible to the naked eye, and at the same time display a strong absorption in the near-infrared range
Data Source
AI summary
The present invention relates to the field of security inks suitable for printing machine readable security features on substrate, security documents or articles as well as machine readable security feature made from said security inks, and security documents comprising a machine readable security feature made from said security inks. In particular, the invention provides security inks comprising one or more IR absorbing materials selected from the group consisting of crystal water-free iron(II) orthophosphates of the general formula Fe3(PO4)2 and having a graftonite crystal structure, crystal water-free iron(II) metal orthophosphates, crystal water-free iron(II) metal phosphonates, crystal water-free iron(II) metal pyrophosphates, crystal water-free iron(II) metal metaphosphates of the general formula FeaMetb(POc)d, wherein said security ink is an oxidative drying security ink, a UV-Vis curable security ink, a UV-Vis curable security ink or a combination thereof.