Dithiolene Metal Complexes for Colorless IR Absorption
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Solution Overview
Problem
Current IR absorbers lack satisfactory colorlessness and simultaneously fail to meet requirements of heat and light stability, particularly in applications like security printing and laser-welding of plastics.
Innovation Solution
The use of heterocyclic dithiolene metal complexes, specifically compounds of formula I and II, which act as colorless IR absorbers, offering superior colorlessness while maintaining heat and light stability, and can be incorporated into plastics for laser-welding and used in security printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional IR absorbers (quinone-diimmonium salts, polymethines, phthalocyanines) are used to achieve IR absorption, then IR absorption function is provided, but visible coloration occurs and colorlessness is compromised
Solution Approach 1:
The patent changes the chemical parameters by introducing dithiolene metal complexes with specific metal centers (Ni, Pd, Pt, Au, Ir, Fe, Zn, W, Cu, Mo, In, Mn, Co, Mg, V, Cr, Ti) and heterocyclic ligand structures. This parameter change in molecular structure enables IR absorption while maintaining colorlessness by adjusting the electronic transitions to occur in the IR region rather than the visible region.
Solution Approach 2:
The patent employs composite structures by combining metal centers with heterocyclic dithiolene ligands containing specific substituent groups (R1-R6). This composite molecular architecture achieves both IR absorption capability and colorlessness, resolving the contradiction between functional performance and aesthetic appearance.
2Illumination intensity
If IR absorbers are designed to be colorless, then colorlessness is improved, but heat stability and light stability are compromised
Solution Approach 1:
The patent applies local quality by introducing specific stabilizing substituent groups (R1-R6) at particular positions on the heterocyclic dithiolene ligand framework. These localized structural modifications enhance overall molecular stability and resistance to heat and light degradation while preserving the colorless property and IR absorption capability.
Solution Approach 2:
The patent modifies molecular parameters by selecting specific metal centers and ligand configurations that inherently provide greater thermal and photostability. The heterocyclic dithiolene structure with appropriate substituents creates a more robust molecular framework that resists degradation under heat and light exposure while maintaining colorlessness.
3Ease of operation
If existing IR absorbers are used for security printing applications, then IR readability is achieved, but fastness to light is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters by using dithiolene metal complexes with specific electronic structures that provide both strong IR absorption for readability and high photostability for light fastness. The metal-dithiolene charge transfer transitions are tuned to the IR region, ensuring readability while the robust molecular structure provides resistance to photodegradation.
Solution Approach 2:
The patent uses composite molecular structures combining stable metal centers with heterocyclic dithiolene ligands featuring stabilizing substituents. This composite architecture provides both the IR absorption necessary for readability and the structural integrity required for excellent light fastness in security printing applications.
4Ease of manufacture
If conventional IR absorbers are incorporated into plastics for laser-welding, then IR absorption for welding is provided, but heat stability during processing is insufficient
Solution Approach 1:
The patent modifies the thermal parameters by incorporating dithiolene metal complexes with high thermal stability into the plastic matrix. The metal-dithiolene coordination bonds and heterocyclic structure provide resistance to thermal degradation during laser-welding processing, maintaining structural integrity at elevated temperatures while enabling IR absorption for welding functionality.
Solution Approach 2:
The patent creates a composite system by integrating thermally stable dithiolene metal complex molecules within the plastic material. This composite approach ensures that the IR absorber maintains its structural stability and functional performance under the high temperature conditions encountered during laser-welding operations.
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
These dithiolene metal complexes provide effective IR absorption without visible color, ensuring excellent fastness to light and heat stability, enabling their use in various applications including security printing and laser-welding of plastics with improved performance.
Implementation Method 1
Colorless, or at least barely colored, IR absorbers meet a significant technical need... These dithiolene metal complexes provide effective IR absorption without visible color
Data Source
AI summary
The invention relates to the use of compounds of formulae (I) and/or (II) as colorless 1R absorbers wherein M is Ni, Pd, Pt, Au, Ir, Fe, Zn, W, Cu, Mo, In, Mn, Co, Mg, V, Cr or Ti, X1, X2 and X3 are each independently of the others sulfur or oxygen, R1, R2, R3, R4, R5 and R6 are each independently of the others hydrogen, NR7R8, unsubstituted or substituted C1-C18alkyl, C1-C18 alkyl wherein the alkylene chain is interrupted with oxygen, unsubstituted or substituted C1-C18alkenyl, unsubstituted or substituted aryl, unsubstituted or substituted arylalkyl or unsubstituted or substituted heteroarylalkyl, R7 and R8, each independently of the other, being unsubstituted or substituted C1-C18alkyl, unsubstituted or substituted aryl, unsubstituted or substituted arylalkyl or unsubstituted or substituted heteroarylalkyl, a further IR absorber optionally being added to the compounds of formulae (I) and (II). The invention relates also to novel dithiolene compounds of formulae (I) and (II) wherein X1 is oxygen and X2 and X3 are oxygen or sulfur. The invention relates furthermore to novel dithiolene compounds of formulae (I) and (II) wherein R1 to R6 are NR7R8.