Monomer Composition for Oxygen-Resistant UV Curing

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Solution Overview

Problem

Cationically-curable inks with divinyl ether compounds are unsuitable due to moisture absorption, leading to cure inhibition and curing failure in humid conditions, while radically-curable inks suffer from oxygen inhibition and poor substrate adhesion.

Innovation Solution

A monomer composition containing a multifunctional vinyl ether compound, a bifunctional oxetane compound with an aromatic ring skeleton, and a monofunctional oxetane compound, along with an epoxy compound, which allows for rapid curing under UV irradiation even in the presence of oxygen and water, with excellent substrate adhesion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If cationically-curable inks contain divinyl ether compound having a cyclic ether skeleton, then substrate adhesion is improved, but the ink becomes susceptible to cure inhibition by water and undergoes curing failure in humid conditions

Engineering Contradiction:

Improvesubstrate adhesionVSAvoidcure reliability in humid conditions

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent changes the chemical parameters of the vinyl ether compound by specifying precise structural requirements: the cyclic ether skeleton must contain 3-8 membered rings with specific heteroatom compositions (1-3 heteroatoms from O, N, S). This parameter optimization maintains the adhesion benefits while reducing moisture susceptibility by selecting ring sizes and heteroatom combinations that balance polarity and steric protection.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite monomer system by combining the optimized cyclic vinyl ether compound with specific counterions (from BF4-, PF6-, CF3SO3-, etc.) to form a cationic photopolymerization initiator complex. This composite approach allows the vinyl ether compound to provide adhesion while the counterion system manages the polymerization kinetics and moisture resistance, achieving both adhesion and cure reliability.

Inventive Principle:

Principle #40Composite materials

2Speed

If radically-curable inks are used, then rapid curability is achieved, but the inks suffer from cure inhibition by oxygen and have poor substrate adhesion

Engineering Contradiction:

Improvecurability speedVSAvoidsubstrate adhesion

Core Design Contradiction:

SpeedVSStrength

Solution Approach 1:

The patent replaces the radical-based curing mechanism with a cationic photopolymerization mechanism. This substitution fundamentally changes the chemistry from radical reactions (which are oxygen-sensitive) to cationic reactions (which are not oxygen-sensitive and provide better adhesion). The use of cyclic vinyl ether compounds with specific heteroatom-containing skeletons enables this mechanism transition while maintaining rapid curability through optimized ring strain and heteroatom effects on polymerization rate.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If low-viscosity inks are used for inkjet recording, then dischargeability is improved, but oxygen diffusion into the ink is facilitated causing cure inhibition

Engineering Contradiction:

ImprovedischargeabilityVSAvoidoxygen inhibition

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent inverts the approach to oxygen inhibition: instead of trying to prevent oxygen from entering the low-viscosity ink (which would compromise dischargeability), it uses a cationic polymerization chemistry that is inherently insensitive to oxygen presence. This inversion allows the ink to maintain low viscosity for excellent dischargeability while the cationic mechanism ignores the oxygen that inevitably diffuses in, eliminating the trade-off between dischargeability and cure effectiveness.

Inventive Principle:

Principle #13The other way round (Inversion)

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 curable composition achieves rapid curing and excellent substrate adhesion, resisting moisture absorption and oxygen inhibition, resulting in improved storage stability and reduced residual monomers and odors, making it suitable for UV-curable inkjet inks.

Implementation Method 1

can be rapidly cured by ultraviolet irradiation

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Data Source

PatentEP3162854B1Monomer composition and curable composition containing same

Publication Date: 2020.04.15 DAICEL CORP

AI summary

Provided is a monomer composition that has rapid curability and can be rapidly cured even in the presence of oxygen and/or water, to form a cured product having excellent adhesion to a wide variety of substrates. The monomer composition according to the present invention contains a multifunctional vinyl ether compound in an amount of 10 to 80 weight percent, a bifunctional oxetane compound represented by Formula (b) in an amount of 0.5 to 20 weight percent, and a monofunctional oxetane compound represented by Formula (b') in an amount of 5 to 80 weight percent. In the formulae, Ring Z is selected from an aromatic hydrocarbon ring and a structure including two or more aromatic hydrocarbon rings bonded to each other through a single bond or a linkage group; R represents a monovalent aliphatic hydrocarbon group; R' is selected from hydrogen and ethyl; and m represents an integer of 0 or more.