Radiation-Curable Inkjet Ink Set for Adhesion Without Nozzle Blocking
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Solution Overview
Problem
Radiation curable inkjet inks face challenges in achieving good adhesion to non-absorbing substrates like polypropylene (PP) and polymethylmethacrylate (PMMA) while maintaining curing speed and avoiding stickiness issues, with existing solutions often causing nozzle blockages and compromising ink properties.
Innovation Solution
A radiation curable inkjet ink set comprising specific monomers and oligomers within narrow ranges, along with photoinitiators, to achieve optimal adhesion and minimize stickiness on PP and PMMA substrates without using low-boiling point solvents, ensuring reliable jetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If low-boiling point solvents like methyl acetate are used to improve adhesion on polypropylene substrates, then adhesion is improved, but nozzle blockages occur due to solvent evaporation
Solution Approach 1:
The patent removes low-boiling point solvents (methyl acetate, ethyl acetate) from the ink composition entirely. Instead, it uses high-boiling point solvents (ethyl lactate, propylene carbonate) that do not evaporate from print head nozzles, thereby eliminating nozzle blockages while maintaining adhesion through alternative mechanisms (polymerizable compounds and surfactants).
Solution Approach 2:
The patent changes the boiling point parameter of the solvent from low (57°C for methyl acetate) to high (>100°C for ethyl lactate and propylene carbonate). This parameter change prevents evaporation during storage and jetting operations, eliminating nozzle blockages while maintaining ink performance.
2Strength
If a mixture of monomers is used to achieve adhesion on multiple substrates, then adhesion is improved, but dispersion stability and curing sensitivity deteriorate
Solution Approach 1:
The patent assigns different functional roles to specific monomers rather than using a broad mixture. N-vinyl caprolactam (10-40 wt%) specifically targets polypropylene adhesion through swelling, while isobornyl acrylate (30-60 wt%) provides general adhesion and curing. This specialized assignment maintains dispersion stability while achieving multi-substrate adhesion.
Solution Approach 2:
The patent creates a composite monomer system combining N-vinyl caprolactam and isobornyl acrylate in specific ratios. This composite approach leverages the swelling capability of N-vinyl caprolactam for polypropylene and the adhesion properties of isobornyl acrylate, achieving broad substrate compatibility while maintaining ink stability.
3Strength
If high amounts of monofunctional monomers are used to achieve adhesion, then adhesion is improved, but surface cure issues occur leading to stickiness
Solution Approach 1:
The patent changes the functional distribution parameter by using predominantly monofunctional monomers (90-99 wt% of total polymerizable compounds) but selects specific types (isobornyl acrylate, N-vinyl caprolactam) that provide both adhesion and adequate surface cure. This parameter optimization achieves adhesion without excessive stickiness.
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 set provides improved adhesion and prevents stickiness on a variety of substrates, ensuring reliable jetting and high curing speed, suitable for industrial environments.
Implementation Method 1
Radiation curable inkjet inks are cured by UV irradiation, which initiates polymerization of monomers and oligomers present in the ink
Implementation Method 2
The ink composition comprises polymerizable compounds and a photoinitiating system, wherein the polymerizable compounds are cured by UV irradiation
Data Source
AI summary
A radiation curable inkjet ink set comprising a cyan inkjet ink containing a beta-copper phthalocyanine pigment and a polymerizable composition; a magenta inkjet ink containing a magenta or red pigment and a polymerizable composition; a yellow inkjet ink containing a yellow pigment and a polymerizable composition; and a black inkjet ink containing a carbon black pigment and a polymerizable composition; wherein the polymerizable compositions of the cyan, magenta, yellow and black inkjet inks include on average: a) 20.0 to 40.0 wt% of phenoxyethyl acrylate; b) 23.0 to 32.0 wt% of isobornyl acrylate; c) 1.0 to 14.4 wt% of monomer selected from the group consisting of 4-acryloylmorpholine and a monomer according to Formula (I), wherein X represents C or O, n represents 1, 2 or 3 and m represents 0 or 1; and d) up to 14.0 wt% of a multifunctional monomer or oligomer; wherein all weight percentages (wt%) are based upon the total weight of the inkjet ink; and wherein 0, 1 or 2 of the cyan, magenta, yellow and black inkjet inks deviate in a range a) to d) and this deviation is no more than 1.0 wt%.