UV-Curable Inkjet Ink Composition for Fast Cure and Adhesion
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Solution Overview
Problem
Existing inkjet inks struggle to achieve high cure speeds required for high-speed printing applications while maintaining high-quality images, as the inclusion of multifunctional monomers and radiation-curable oligomers leads to issues like film shrinkage and substrate embrittlement, and monofunctional monomers reduce cure speed.
Innovation Solution
Inkjet ink formulation comprising 5-40% N-vinyl monomers (e.g., N-vinyl caprolactam, N-vinyl pyrrolidone) and restricted amounts of difunctional and monofunctional monomers with (meth)acrylate groups, along with a photoinitiator, to balance cure speed and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multifunctional monomers are included to increase cure speed, then cure speed is improved, but viscosity increases and adhesion deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters by introducing N-vinyl monomers with specific functional groups that cure rapidly while maintaining flexible polymer chains. This parameter change allows achieving high cure speed without the excessive viscosity and poor adhesion associated with traditional multifunctional monomers.
Solution Approach 2:
The patent creates a composite ink formulation combining N-vinyl monomers with difunctional and monofunctional monomers in specific ratios. This composite approach leverages the fast-curing property of N-vinyl monomers while the other monomers provide flexibility and adhesion, resolving the contradiction between cure speed and mechanical properties.
2Strength
If monofunctional monomers are included to offset film shrinkage, then adhesion is improved, but cure speed decreases
Solution Approach 1:
The patent changes the monomer selection parameter by using N-vinyl monomers instead of traditional monofunctional monomers. N-vinyl monomers provide the necessary flexibility and adhesion while maintaining rapid curing capability, thus improving adhesion without sacrificing cure speed.
Solution Approach 2:
The patent finds an alternative (N-vinyl monomer) that copies the beneficial effects of monofunctional monomers (flexibility and adhesion) while avoiding their detrimental effect (slow curing). This substitution allows achieving both improved adhesion and maintained fast cure speed.
3Speed
If radiation-curable oligomers are included to increase cure speed, then cure speed is improved, but film shrinkage increases causing substrate embrittlement
Solution Approach 1:
The patent changes the oligomer selection parameter by choosing radiation-curable oligomers with specific molecular weights and functional group densities. This parameter change enables fast curing while controlling film shrinkage to prevent substrate embrittlement.
Solution Approach 2:
The patent applies local quality control by carefully selecting and proportioning specific types of oligomers and monomers in different regions of the ink formulation. This localized optimization ensures fast curing where needed while minimizing shrinkage effects throughout the printed film.
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 achieves fast cure speeds without compromising image quality, with improved flexibility and adhesion, by using a specific blend of N-vinyl monomers and controlled monomer amounts.
Implementation Method 1
Another type of inkjet ink contains unsaturated organic compounds, termed monomers and/or oligomers which polymerise by irradiation, commonly with ultraviolet light, in the presence of a photoinitiator.
Data Source
AI summary
The present invention provides an inkjet ink comprising: 5-40% by weight of an N-vinyl monomer selected from N-vinyl caprolactam, N-vinyl pyrrolidone, N-vinyl piperidone, N-vinyl carbazole, N-vinyl formamide, N-vinyl indole, N-vinyl imidazole, N-vinyl acetamide, and mixtures thereof, based on the total weight of the ink; one or more difunctional monomers in which the only radiation-curable functional groups present in the monomer are (meth)acrylate groups; 9% or less by weight of a monofunctional monomer, other than the N-vinyl monomer, together with a multifunctional monomer, based on the total weight of the ink; a radical photoinitiator; and a colouring agent. The present invention also provides a method of inkjet printing using the inkjet ink of the present invention and use of an N-vinyl monomer selected from N-vinyl caprolactam, N-vinyl pyrrolidone, N-vinyl piperidone, N-vinyl carbazole, N-vinyl formamide, N-vinyl indole, N-vinyl imidazole, N-vinyl acetamide, and mixtures thereof to increase the cure speed of an inkjet ink comprising one or more of difunctional monomers.