Low Migration Energy Curable Inks for UV LED Curing
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Solution Overview
Problem
Conventional UV ink systems are not suitable for high-speed printing with UV LED lamps, as they often fail to cure due to energy absorption by white pigments, leading to incomplete photopolymerization and potential contamination from residual monomers and photodecomposition products, particularly in food packaging applications.
Innovation Solution
The development of energy curable ink and coating compositions comprising 2-30 wt% 3-methyl-1,5-pentanediol diacrylate, photoinitiators, optical brightening agents, and minimal organic solvents, optimized for UV LED curing, ensuring low migration and adhesion to flexible substrates, and suitable for various energy curing methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional UV ink systems are used with UV LED lamps, then the printing process can be simplified, but the ink fails to cure properly due to energy absorption by white pigments
Solution Approach 1:
The patent modifies the chemical composition parameters of the ink system by incorporating specific photoinitiators (Types I and II), monomers, and oligomers that are optimized for UV LED wavelengths. This parameter change enables the ink to cure effectively under UV LED lamps despite the presence of white pigments that absorb energy.
2Ease of operation
If high amounts of monofunctional monomers are used in cured inks, then the ink achieves good printability and flow, but residual monomers migrate and contaminate the packaged product
Solution Approach 1:
The patent creates a composite monomer system combining monofunctional and multifunctional monomers/oligomers. This composite approach allows the ink to maintain good printability from the monofunctional components while the multifunctional components provide crosslinking that reduces residual monomer content and migration, thus eliminating contamination.
3Object-affected harmful factors
If UV LED lamps are used for curing, then heat generation and ozone production are reduced, but the ink must be optimized for specific wavelengths which limits compatibility
Solution Approach 1:
The patent develops a universal ink formulation that can be cured by multiple energy sources including UV LED lamps, conventional UV lamps, and electron beam irradiation. The ink system incorporates photoinitiators and monomers that respond to different wavelengths and energy types, making it adaptable to various curing technologies while maintaining the benefits of reduced heat and ozone generation.
4Quantity of substance
If white pigment is added to achieve opaque white ink, then coverage and opacity are improved, but energy absorption increases preventing proper curing
Solution Approach 1:
The patent introduces photoinitiators as intermediary substances that absorb UV LED energy and transfer it to trigger polymerization. These photoinitiators act as mediators between the UV LED light source and the monomer/oligomer system, enabling curing to proceed even in the presence of white pigments that would otherwise block the energy transfer.
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 ink and coating compositions achieve excellent cure, printability, and resistance to isopropanol rubs, with high adhesion to flexible substrates, while minimizing contamination and ensuring effective curing across different energy curing technologies, including UV LED, standard UV, and electron beam.
Implementation Method 1
Energy curable inks and coatings are often used in the printing of food packaging... Energy curing is faster and more efficient than conventional curing means... UV LED (light emitting diode) chip technology has grown considerably... wavelengths important for photo-polymerization of UV-sensitive inks
Implementation Method 2
the optical brightening agent is a fluorescent brightening agent
Data Source
AI summary
The present invention provides energy curable ink and coating compositions that comprise polymerizable compounds, photoinitiators, and colorants. The polymerizable compounds comprise one or more polymerizable monomers and/or oligomers, wherein at least a portion is 3-methyl-1,5-pentanediol diacrylate. The inks and coatings of the invention exhibit excellent print properties after UV-LED, standard UV mercury vapor lamp, and electron beam cure.