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Q: Why is viscosity so important in UV inkjet ink?
A: UV inkjet ink has to pass through very small printhead nozzles and form stable droplets during high-speed printing. If the viscosity is too high, the ink may have difficulty jetting, which can lead to misfiring, unstable droplets, nozzle clogging, or inconsistent print quality. Viscosity changes during storage or printing can also affect process stability.
For this reason, viscosity should be considered early when developing UV inkjet ink. However, reducing viscosity is not simply a matter of adding more diluent. The UV resin, reactive monomers, photoinitiator, additives, pigments, and curing conditions all contribute to the final formulation behavior.
Q: How does UV resin affect the viscosity of UV inkjet ink?
A: UV resin is one of the primary film-forming components in a UV-curable formulation, so its viscosity can have a substantial effect on the overall ink system.
One practical approach is to start with a resin specifically designed for low-viscosity applications. A lower-viscosity oligomer may reduce the amount of reactive diluent needed while still contributing to film formation, adhesion, flexibility, hardness, and durability.
However, low viscosity by itself does not make a resin suitable for inkjet. The resin must also be compatible with the monomer and pigment system and provide sufficient curing and film performance after printing.
Q: Which low-viscosity UV resins can be considered for inkjet formulations?
A: Several Lencolo UV resin grades are positioned for inkjet applications.
L-6111 is a low-viscosity epoxy acrylate with a viscosity of 250–800 CPS. It is indicated for coatings, inks, inkjet, OPV/PVD, and 3D printing, making it a potential starting point for formulations where viscosity reduction is important.
For polyurethane acrylates, L-6211 has a viscosity of 120–280 CPS and combines ultra-low viscosity with fast curing, flexibility, tear resistance, and good pigment wettability. It is indicated for inkjet, adhesives, OPV, plastics, and peelable or elastic coatings.
L-6211D provides the same 120–280 CPS viscosity range in a non-organotin version. It can be evaluated when an organotin-free resin is required.
L-6212 has an ultra-low viscosity of 25–50 CPS, together with good leveling, flexibility, toughness, and pigment wetting. Its indicated applications include inkjet, adhesives, OPV, plastic, paper, and PVC flooring.
For LED-curable systems, L-6241 has a viscosity of 20–50 CPS and combines low odor, low viscosity, fast LED curing, low shrinkage, toughness, and good film formation. It is also indicated for inkjet applications.
Q: Can replacing a high-viscosity resin with a low-viscosity resin solve the problem by itself?
A: Not always. The entire ink formulation needs to be considered.
Reactive monomers can further adjust viscosity while participating in the cured network. Photoinitiators need to be selected according to the curing technology, while additives can affect flow, leveling, and dispersion. Pigments and fillers can also increase viscosity significantly.
Therefore, a resin that shows 25–50 CPS or 120–280 CPS on a technical data sheet may produce a different viscosity after being combined with pigments, monomers, photoinitiators, and other formulation components.
Q: What should be considered besides viscosity?
A: A UV inkjet formulation needs to balance viscosity with jetting stability, surface tension, pigment dispersion, curing speed, adhesion, flexibility, hardness, scratch resistance, chemical resistance, yellowing, and substrate compatibility.
The curing system is also important. UV LED and mercury UV systems may require different photoinitiator and resin combinations. Printhead type, nozzle temperature, ink temperature, film thickness, and curing energy can further affect actual printing performance.
Q: How should a final low-viscosity resin be selected?
A: Low-viscosity products should be treated as candidate materials rather than automatic final recommendations. The appropriate resin depends on the printhead, target viscosity, pigment concentration, monomer system, curing equipment, substrate, and required cured-film properties.
For example, L-6111, L-6211, L-6211D, L-6212, and L-6241 can provide different starting points for comparative evaluation. The final choice should be confirmed through formulation trials and actual inkjet testing.
The objective is therefore not simply to obtain the lowest possible viscosity. A successful UV inkjet formulation needs a viscosity range that supports stable jetting while maintaining reliable curing, adhesion, flexibility, hardness, and durability after printing.
https://www.lencolo37.com/
Guangdong Lencolo New Material Co., Ltd.
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