UV-LED Curable Ink Composition With Low Photoinitiator Migration
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Solution Overview
Problem
Existing UV-LED curable inks face challenges in achieving non-yellowing, completely-cured, low migration, and skin sensitization, particularly due to the migration of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), which is a known skin sensitizer and violates regulatory criteria for food and pharmaceutical packaging.
Innovation Solution
The development of UV-LED ink compositions using polymeric diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPOL) covalently bound to polymers or non-covalently associated with materials to reduce migration, combined with a matrix system containing chain extension agents, multifunctional crosslinking agents, reactive diluents, and flexibility-inducing materials, eliminating organic solvents and utilizing UV-LED sources for curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TPO photoinitiator is used for UV-LED curing, then complete curing and non-yellowing properties are achieved, but migration to substrate and skin sensitization occur
Solution Approach 1:
The patent uses a composite photoinitiator system combining TPO with a polymer matrix (epoxy resin or polyether) to create a hybrid material that maintains the photoinitiating activity of TPO while the polymer component provides a higher molecular weight structure that reduces migration. This composite approach allows the system to achieve complete curing and non-yellowing properties while minimizing skin sensitization risks.
Solution Approach 2:
The patent changes the molecular weight parameter of the photoinitiator system by incorporating TPO into a polymer matrix. The polymer component has a significantly higher molecular weight than free TPO, which reduces its mobility and migration tendency. This parameter change maintains the photoinitiating function while reducing the harmful migration effect.
2Productivity
If TPO photoinitiator is used, then effective UV-LED curing is achieved, but migration to label and substrate occurs
Solution Approach 1:
The patent creates a composite photoinitiator system where TPO is combined with a polymer matrix (epoxy resin or polyether). The polymer component provides a higher molecular weight structure that reduces migration while maintaining the photoinitiating activity of TPO. This composite structure prevents TPO from migrating to the label or substrate while preserving fast curing speed.
Solution Approach 2:
The polymer matrix (epoxy resin or polyether) acts as an intermediary carrier for the TPO photoinitiator. Instead of using free TPO that can migrate, the polymer serves as a medium that holds TPO in place while still allowing it to perform its photoinitiating function under UV-LED irradiation. This intermediary structure prevents migration while maintaining curing effectiveness.
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 compositions achieve low migration and minimal skin sensitization, with residual TPOL reduced by up to 200 ppm, enhancing productivity and environmental benefits through instant curing with minimal heat and ozone production.
Implementation Method 1
the one or more materials are polymerized, crosslinked, and/or cured upon exposure to the UV-LED source
Data Source
AI summary
UV-LED ink composition compositions containing a matrix or binder system, one or more colorants, and one or more photo-initiators. In some embodiments, the matrix or binder system is cured using one or more UV-LED sources. In some embodiments, the matrix or binder system contains one or more materials that are polymerized, crosslinked, and/or cured upon exposure to the UV-LED source. This allows the ink composition to be free of any organic solvents. After polymerization and/or crosslinking, the ink is dry. UV-LED ink compositions can be better suited for curing black inks, improve/increase productivity due to its instant on/instant off capability, and produce little or no heat. Such compositions may have environmental benefits as well as the curing process does not produce ozone and requires less exhaust air surrounding the press.