Inkjet Ink Sol-Gel Phase Transition for Nozzle Clogging
Solution Overview
Problem
Ultraviolet radiation-curable ink-jet systems face issues with local thermal polymerization reactions that lead to nozzle clogging, which cannot be effectively inhibited by adding polymerization inhibitors, necessitating an ink that avoids such reactions for improved ejection stability.
Innovation Solution
An actinic radiation-curable ink-jet ink formulation incorporating specific photopolymerizable compounds and a gelling agent, with a compound B content of 5-15% of compound A, and a gelling agent concentration of 0.5-7.0% by total mass, that undergoes temperature-dependent reversible sol-gel phase transition, preventing local thermal polymerization and ensuring stable ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the ink is heated to exceed 50°C to achieve liquid state for ejection, then the ink can be ejected from the ink-jet head, but local thermal polymerization reaction occurs causing nozzle clogging
Solution Approach 1:
The patent changes the chemical parameters of the ink formulation by specifying precise molecular weight ranges (280-1500) for photopolymerizable compounds, controlling hydroxyl group content (5-15 mass%), and setting gelling agent concentration (0.5-7.0 mass%). These parameter changes enable the ink to maintain stability at high temperatures while preventing thermal polymerization, thus resolving the contradiction between ejection capability and nozzle stability.
Solution Approach 2:
The patent creates a composite ink system combining photopolymerizable compounds with specific molecular weights, hydroxyl-containing compounds at controlled ratios, photoinitiators, and gelling agents. This composite formulation works synergistically to prevent local thermal polymerization while maintaining ejection performance, resolving the contradiction between speed and reliability.
2Reliability
If a polymerization inhibitor is added to prevent thermal polymerization, then polymerization can be inhibited, but it cannot effectively prevent local thermal polymerization and may compromise curing performance
Solution Approach 1:
Instead of using polymerization inhibitors that may compromise curing, the patent converts the potential harm of thermal polymerization into a benefit by designing a formulation where the photopolymerizable compounds themselves resist thermal polymerization through their specific molecular weight and structural characteristics. The hydroxyl groups and gelling agents work synergistically to stabilize the ink thermally while maintaining excellent UV curing performance, thus converting the problem of polymerization control into a solution that enhances both stability and curing quality.
3Reliability
If the gelling agent concentration is increased to prevent polymerization, then ejection stability improves, but the ink may not maintain satisfactory physical properties of cured film
Solution Approach 1:
The patent optimizes the gelling agent concentration parameter within the specific range of 0.5-7.0 mass%, which is sufficient to provide thermal stability and prevent polymerization during ejection but not so high as to compromise cured film properties. This precise parameter control resolves the contradiction between ejection stability and film strength by finding the optimal balance point.
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 ink exhibits enhanced ejection stability and maintains satisfactory physical properties of the cured film, preventing nozzle clogging and ensuring reliable high-speed image formation without compromising image quality.
Implementation Method 1
an actinic radiation-curable ink-jet ink that undergoes temperature-dependent reversible sol-gel phase transition
Implementation Method 2
comprising a photopolymerizable compound, a photoinitiator
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
Provided are an active-energy-ray-curing inkjet ink which has excellent discharge stability and does not cause a local thermal polymerization reaction, and an image formation method using the same. The present invention pertains to an active-light-curing inkjet ink which contains a photopolymerizable compound, a photoinitiator, and a gelling agent, and which undergoes a reversible sol-gel phase transition due to temperature, wherein the photopolymerizable compound contains one or more combinations of: a compound (A) having at least n number (n being an integer of 2 or greater) of (meth)acrylate ester units, represented by the indicated formula, and having a molecular weight in the range of 280-1500; and a compound (B) having n-1 number of (meth)acrylate ester units and a hydroxyl group, represented by the indicated formula, and having a molecular weight in the range of 280-1500 (In the formula, n represents an integer of 2 or more, and R repres - ents n number of hydrocarbon groups which may be branched, are straight-chain-shaped or ring-shaped, and may contain an oxygen atom or a nitrogen atom. n is the same integer and R represents the same structure in both compounds (A and B).) Furthermore, in the one or more combinations of the compound (A) and the compound (B), the amount of the compound (B) contained is 5-15 mass% of the total mass of the compound (A) corresponding to the compound (B), the amount of the gelling agent contained is 0.5-7.0 mass% in relation to the total mass of the ink, and the gelling temperature is 50°C or higher.