Functionalized Acyl Phosphine Oxide Initiators for UV Inkjet Surface Cure
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Solution Overview
Problem
UV curable inkjet inks using acyl phosphine oxide initiators suffer from insufficient surface cure and odor issues, particularly in LED curing, which can lead to unacceptable physical properties and health risks, and the use of oxygen depletion units complicates printer design and increases costs.
Innovation Solution
Incorporating acyl phosphine oxide initiators substituted by a tertiary amine at a specific position near the phosphorus atom, with functional groups like urea or oxalyl amide, and limiting the molecular weight to no more than 3000, to enhance surface cure and reduce odor without requiring oxygen depletion units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If standard acyl phosphine oxide initiators are used for LED curing, then curing efficiency is improved, but volatile aldehydes are formed causing bad smell and health risks
Solution Approach 1:
The patent modifies the molecular structure of acyl phosphine oxide initiators by substituting the mesityl group with functionalized groups (urea, oxalyl amide, tertiary amine) at specific positions. This chemical parameter change eliminates the formation of volatile aldehydes during curing while maintaining LED curing efficiency, thus resolving the contradiction between productivity and harmful emissions.
2Power
If conventional acyl phosphine oxide initiators are used, then LED curing is effective, but surface cure is insufficient leading to residual uncured monomers
Solution Approach 1:
The patent introduces functional groups at specific local positions (ortho positions) of the acyl phosphine oxide initiator structure. These localized modifications create specific interactions that enhance surface cure quality without compromising the overall LED curing effectiveness, resolving the contradiction between power and reliability.
3Reliability
If oxygen depletion units are implemented to improve surface cure, then curing quality is improved, but printer complexity and cost increase
Solution Approach 1:
The modified acyl phosphine oxide initiators inherently provide improved surface cure properties through their molecular structure, eliminating the need for external oxygen depletion units. The initiators self-adjust their reactivity to overcome oxygen inhibition at the surface, thus achieving reliable curing without adding complex equipment.
4Object-generated harmful factors
If molecular weight of photoinitiator is increased, then odor is reduced, but oxygen inhibition becomes more pronounced and curing speed decreases
Solution Approach 1:
The patent optimizes the molecular weight parameter of the acyl phosphine oxide initiator to a specific range (500-3000 Da) and combines it with specific functional group substitutions. This parameter optimization achieves a balance where odor is sufficiently reduced while maintaining fast curing speed by preventing excessive oxygen inhibition.
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 solution provides improved surface cure properties and reduces odor in UV curable inkjet inks, allowing for efficient printing under ambient conditions with enhanced printer design simplicity and cost-effectiveness.
Implementation Method 1
UV curable inkjet inks including a free radical polymerizable compound and an acyl phosphine oxide initiator
Implementation Method 2
UV curing the jetted UV curable inkjet ink using UV LEDs having an emitting wavelength between 365 nm and 400 nm
Data Source
AI summary
A UV curable inkjet ink including a free radical polymerizable compound and an acyl phosphine oxide initiator wherein the acyl phosphine oxide initiator includes an acyl group selected from the group consisting of a benzoyl group substituted by an urea group or an oxalylamide group; a 2,6-dimethyl benzoyl group substituted in position 3 by an urea group or an oxalylamide group; a 2,6-dimethoxy benzoyl group substituted in position 3 by an urea group or an oxalylamide group; a 2,4,6-trimethyl benzoyl group substituted in position 3 by an urea group or an oxalylamide group; and a 2,4,6-trimethoxybenzoyl group substituted in position 3 by an urea group or an oxalylamide group wherein the urea group and the oxalylamide group include a tertiary amine group positioning a phosphorus atom of the acylphosphine oxide initiator in a 1 to Z position, where position 1 is defined as that of the phosphorus atom and position Z is defined as the nitrogen atom of the tertiary amine group with Z representing an integer of at least 11; and that the acyl phosphine oxide initiator contains no more than two photoinitiating moieties having a phosphine oxide group.