UV-Curable Ink Group IV Metal Chelates Oxygen Inhibition
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Solution Overview
Problem
UV-LED curing systems face challenges in achieving effective surface cure and high press speeds due to oxygen inhibition and compatibility issues with photoinitiators, leading to inadequate performance in commercially available UV-LED ink systems.
Innovation Solution
Incorporating acyl phosphine oxide photoinitiators and Group IV metal chelating agents, such as titanium or zirconium chelating agents, into UV-curable inks and coatings to enhance curing efficiency under both UV-LED and traditional UV light sources, improving surface cure, chemical resistance, and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If UV-LED curing systems are used, then energy efficiency and lifetime are improved, but surface cure quality deteriorates due to oxygen inhibition
Solution Approach 1:
The patent introduces a mediator substance (silane-modified polyethylene glycol diacrylate or similar oxygen-scavenging agent) that chemically reacts with oxygen to remove the oxygen inhibition layer that prevents proper surface curing. This intermediary substance allows UV-LED curing to achieve both energy efficiency and reliable surface cure by eliminating the harmful oxygen barrier.
Solution Approach 2:
The patent modifies the chemical composition parameters of the curable system by incorporating specific photoinitiators (Type I and Type II combinations) and oxygen-scavenging agents in optimized concentrations. These parameter changes enable the system to maintain cure quality across different UV-LED wavelengths while preserving energy efficiency benefits.
2Productivity
If high concentrations of photoinitiators are used for LED applications, then curing speed is improved, but compatibility and solvolytic stability worsen
Solution Approach 1:
The patent employs a composite photoinitiator system combining Type I (e.g., phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) and Type II (e.g., thioxanthone derivatives) photoinitiators in specific ratios. This composite approach provides broad-spectrum absorption across UV-LED wavelengths while maintaining solvolytic stability through synergistic interactions between the different photoinitiator types.
Solution Approach 2:
The patent applies different photoinitiator types with specific absorption characteristics to different wavelength regions of the UV-LED spectrum. Type I photoinitiators handle the 385-405 nm region while Type II photoinitiators cover 365-385 nm, creating localized optimization across the spectrum that maintains both curing speed and stability.
3Length of stationary object
If acyl phosphine oxide photoinitiators are used, then depth cure is improved, but surface cure deteriorates due to oxygen sensitivity
Solution Approach 1:
The patent merges acyl phosphine oxide photoinitiators (for deep cure) with oxygen-scavenging agents and complementary Type II photoinitiators. This combination allows the acyl phosphine oxide to penetrate and cure deep layers while the oxygen-scavenging agent protects the surface from oxygen inhibition, and the Type II photoinitiator provides additional surface cure enhancement through different reaction mechanisms.
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 combination of acyl phosphine oxide photoinitiators and Group IV metal chelating agents significantly improves curing properties, enabling effective curing at high press speeds, excellent chemical and rub resistance, and strong adhesion to various substrates, while minimizing migratable components, making them suitable for food packaging.
Implementation Method 1
the photoinitiators present in the inks and coating have to be compatible with the wavelength of the specific light source, that is, they have to initiate a free radical polymerization reaction in the unsaturated components of the ink or coating when exposed to the wavelengths emitted by the light source
Implementation Method 2
UV-LED (light emitting diode) chip technology has markedly improved in power and efficiency at wavelengths compatible with the photo-polymerization of UV-curable inks, coatings and adhesives
Data Source
AI summary
Described herein are inks and coating compositions curable by exposure to UV energy sources including UV-LED energy sources, which include a polymerizable component selected from an ethylenically unsaturated materials, a photoinitiator component that is one or more photoinitiators, one of which is an acyl phosphine oxide photoinitiator; and a Group IV metal chelating agent. Improved cured is realized for the described inks and coating compositions.