Radiation-Curable Inkjet Ink Stray Light Resistance
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Solution Overview
Problem
Inkjet inks face issues with stray light resistance and stability due to unwanted polymerization, especially when contaminated with water or solvents, which affects their performance and shelf-life.
Innovation Solution
The inclusion of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (OHT) in combination with photoinitiators such as ethyl (2,4,6-trimethylbenzoyl) phenyl phosphinate and polymeric phosphine oxide photoinitiators in radiation-curable inkjet inks enhances stray light resistance and stability, even in the presence of contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If radiation-curable materials are used in inkjet inks to enable rapid curing, then curing speed is improved, but the inks become susceptible to unwanted polymerization on exposure to stray light
Solution Approach 1:
The patent introduces photoinhibitors as intermediary substances that mediate between the radiation-curable materials and stray light. These photoinhibitors absorb stray light and prevent it from initiating unwanted polymerization, while allowing the intended curing process to proceed efficiently when exposed to the primary UV light source.
Solution Approach 2:
The patent modifies the chemical composition parameters of the ink by incorporating specific photoinhibitors (such as hydroquinone, methyl ether hydroquinone, or butylated hydroxytoluene) at controlled concentrations. This parameter change enables the ink to maintain rapid curing speed while simultaneously improving resistance to stray light-induced polymerization.
2Ease of operation
If water or solvent contamination occurs in the ink, then handling convenience is improved, but ink stability deteriorates and shelf-life is reduced
Solution Approach 1:
The patent incorporates stabilizers and preservatives into the ink formulation beforehand to cushion against the detrimental effects of water or solvent contamination. These additives prevent microbial growth, inhibit viscosity increase, and maintain ink stability even when contamination occurs during handling or storage.
Solution Approach 2:
The patent converts the potential harm of water or solvent contamination into a manageable condition by incorporating specific additives that not only prevent degradation but also allow the ink to maintain acceptable performance characteristics. The contamination, rather than immediately destroying ink stability, is neutralized by the formulated protective agents.
3Reliability
If stray light inhibitors are added to improve stray light resistance, then polymerization control is improved, but ink composition complexity increases
Solution Approach 1:
The patent optimizes the concentration parameters of photoinhibitors to achieve effective stray light resistance at relatively low levels (typically 0.01-5% by weight). This parameter optimization minimizes the impact on overall composition complexity while maintaining reliable polymerization control.
Solution Approach 2:
The patent combines multiple functional components (radiation-curable monomers, oligomers, photoinitiators, and photoinhibitors) into a composite ink formulation where each component works synergistically. This composite approach allows the system to achieve reliable polymerization control through the coordinated action of multiple substances rather than relying on a single complex additive.
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
This combination significantly extends the time to polymerization and maintains ink stability and performance, providing improved cure speed and surface properties even under LED curing, while minimizing surface tack and adhesion issues.
Implementation Method 1
a radiation-curable material, which polymerises when cured... when exposed to actinic radiation, in the presence of a photoinitiator
Implementation Method 2
4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl... stray light inhibitors, such as butylhydroxytoluene (BHT), can be included in the inkjet ink. Such stray light inhibitors reduce polymerisation of the ink on exposure to stray light
Data Source
AI summary
The present invention provides an inkjet ink comprising: a radiation-curable material; 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl; and one or more photoinitiators selected from ethyl(2,4,6-trimethylbenzoyl) phenyl phosphinate, ethyl(3-benzoyl-2,4,6-trimethylbenzoyl)(phenyl) phosphinate, a polymeric phosphine oxide photoinitiator and mixtures thereof. The present invention also provides a method of inkjet printing using the inkjet ink.