NIR-to-Visible Upconverting Inks for Anti-Counterfeiting
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Solution Overview
Problem
Current security printing technologies using UV-to-visible downconversion inks are easily replicable, leading to counterfeiting issues, as they are widely available and simple to reproduce, compromising the authenticity of documents like identity cards and currency.
Innovation Solution
Development of near-infrared (NIR)-to-visible upconverting inks comprising nanocrystals doped with lanthanide metals, such as β-NaYF4, encapsulated in a polymer matrix, which are printed using direct-write or aerosol jet techniques, producing luminescent patterns only visible under NIR light, thus enhancing security features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If UV-to-visible downconversion inks are used for security printing, then the printing process is simple and inexpensive, but the security features are easily replicated and counterfeited
Solution Approach 1:
The patent changes the fundamental optical parameter from UV-to-visible downconversion to NIR-to-visible upconversion. This parameter change makes the ink invisible under normal lighting conditions and requires specific NIR excitation light to reveal the pattern, thereby enhancing security while maintaining manufacturing simplicity
Solution Approach 2:
The patent uses composite upconversion nanocrystal materials embedded in a polymer matrix. These nanocrystals contain multiple rare earth ions (e.g., Yb3+, Er3+, Tm3+) that work together to achieve efficient NIR-to-visible upconversion, creating a material that is both sophisticated for security purposes and printable with simple processes
2Reliability
If photopatterned microstructure films are used for NIR-to-visible upconversion security, then counterfeit protection is enhanced, but the manufacturing process becomes complex requiring three steps
Solution Approach 1:
The patent merges multiple functions into a single printable ink formulation: the nanocrystals provide upconversion, the polymer provides structural matrix and adhesion, and the solvent enables printability. This consolidation allows a complex three-step process to be replaced by a simple one-step direct printing process
Solution Approach 2:
The ink formulation is designed to be self-sufficient, containing all necessary components (nanocrystals, polymer, solvent) in the correct proportions. The ink can be directly printed and dried to form functional upconversion patterns without requiring separate photopatterning or development steps
3Manufacturing precision
If upconversion nanocrystals are used in ink formulation, then high-resolution patterns are achieved, but the ink formulation complexity increases
Solution Approach 1:
The patent optimizes the nanocrystal size parameter to 20-100 nm, which provides the right balance between upconversion efficiency and printability. The size control enables high-resolution patterning while the small size allows the nanocrystals to be well-dispersed in the ink formulation without requiring complex stabilization
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 NIR-to-visible upconverting inks provide a sophisticated security solution that is difficult to replicate, as they require specific NIR excitation, offering high-resolution, multi-color patterns without the need for post-processing, thereby enhancing counterfeit protection and authentication.
Implementation Method 1
upconversion phosphors that can efficiently upconvert near-infrared (NIR) light into visible and NIR luminescence
Implementation Method 2
the nanocrystals are capped with an organic ligand
Implementation Method 3
the ink is formed by mixing the nanocrystals with a polymer in a solvent capable of dissolving the polymer and dispersing the nanocrystals
Implementation Method 4
The ink can be printed and/or written and then deposited to form a film
Data Source
AI summary
The present invention relates generally to using upconverting inks for producing highly-resolved patterns for inter alia, security applications. More specifically, the present invention relates to the use of sols (inks) and printing processes that produce well-defined printed features consisting of polymers impregnated with luminescent upconversion nanocrystals. The patterns printed using such inks and processes may exhibit defined shapes, characters of text, and various other types of images.