Viscosity is one of the most important formulation parameters in UV inkjet printing. Unlike conventional printing inks, UV inkjet formulations must pass through extremely small printhead nozzles and form stable droplets at high printing speeds. Excessive viscosity can affect jetting, while unstable viscosity may contribute to inconsistent droplet formation, nozzle problems, and variations in print quality.
For formulators developing or optimizing UV inkjet inks, reducing viscosity often starts with the selection of the UV resin. However, resin viscosity is only one part of the formulation. Monomers, photoinitiators, additives, pigments, fillers, curing conditions, and the target substrate can all influence the final performance of the ink.
Why Low-Viscosity UV Resin Matters
UV resin is an important film-forming component in a UV-curable ink, and its chemical structure can affect more than viscosity. Resin selection also influences curing behavior, flexibility, hardness, adhesion, scratch resistance, chemical resistance, and other properties of the cured film.
For this reason, choosing a resin specifically designed for low-viscosity applications can provide a more effective starting point than attempting to reduce viscosity only by adding reactive diluents.
A low-viscosity resin can help formulators maintain the flow characteristics required for inkjet printing while leaving more flexibility to optimize other formulation components. The challenge is to reduce viscosity without sacrificing the performance required after curing.
Low-Viscosity Resin Options for UV Inkjet Applications
Guangdong Lencolo New Material Co., Ltd., under the Lencolo brand, offers several UV resin grades positioned for inkjet and other low-viscosity applications. Different resin chemistries provide formulators with options depending on the required balance of viscosity, flexibility, curing speed, pigment wetting, and film performance.
L-6212: Ultra-Low-Viscosity Polyurethane Acrylate
L-6212 is an ultra-low-viscosity, 2-functional polyurethane acrylate with a viscosity range of 25–50 CPS. Its listed characteristics include low viscosity, good leveling, high flexibility, good toughness, and excellent pigment wetting properties.
This combination makes L-6212 a candidate for UV inkjet formulations where extremely low viscosity needs to be combined with flexibility and pigment compatibility. It is also indicated for applications including adhesives, OPV, plastics, paper, and PVC flooring.
L-6211 and L-6211D: Low-Viscosity Polyurethane Acrylates
L-6211 is a 2-functional polyurethane acrylate with a viscosity of 120–280 CPS. It combines ultra-low viscosity with fast curing, good flexibility, tear resistance, and pigment wettability.
L-6211D offers the same viscosity range of 120–280 CPS in a non-organotin version. This provides an alternative for formulators considering organotin-related requirements while maintaining a low-viscosity polyurethane resin option.
Both grades are indicated for inkjet applications as well as adhesives, OPV, plastics, and peelable or elastic coatings.
L-6111: Low-Viscosity Epoxy Acrylate
For formulators evaluating epoxy acrylate chemistry, L-6111 is a low-viscosity UV epoxy acrylate with a listed viscosity range of 250–800 CPS. It is positioned for applications including inks, inkjet, wood, paper, plastics, metals, OPV, PVD, and 3D printing.
Compared with ultra-low-viscosity polyurethane acrylates, an epoxy acrylate option may provide a different route for balancing viscosity with the required cured-film properties.
L-6241: Low-Viscosity Resin for LED UV Curing
UV inkjet systems using LED curing can introduce additional formulation considerations. L-6241 is a low-odor, LED-curable polyurethane acrylate with a viscosity of 20–50 CPS.
Its listed properties include low odor, low viscosity, fast LED curing, low shrinkage, good toughness, and good film formation. It is indicated for inkjet, adhesives, OPV, plastics, paper, and nail gel applications.
Viscosity Reduction Is More Than Resin Selection
Although selecting a low-viscosity UV resin can significantly influence the starting viscosity of an ink, it should not be treated as the only solution.
Reactive monomers may be used to adjust viscosity while also contributing to curing and final film properties. Photoinitiator selection must be compatible with the curing system, particularly when the formulation is designed for UV LED rather than conventional mercury UV curing.
Pigments and fillers can also affect the working viscosity of the final formulation. Additives may influence flow, leveling, wetting, and stability. Therefore, changing the resin without evaluating the rest of the formulation can create a new problem elsewhere, such as reduced flexibility, inadequate adhesion, slower curing, or changes in pigment dispersion.
A successful low-viscosity UV ink is therefore a balance between jetting behavior and cured-film performance.
Match Resin Selection to the Printing System
There is no single low-viscosity resin that is automatically suitable for every UV inkjet formulation. The appropriate candidate depends on the printhead, ink viscosity target, pigment system, curing equipment, substrate, and required film properties.
For example, a formulation prioritizing extremely low viscosity may initially evaluate L-6212 or L-6241, while a system requiring a different balance of flexibility, pigment wetting, and curing may consider L-6211 or L-6211D. L-6111 provides another option for formulators evaluating epoxy acrylate chemistry.
These grades should be considered starting points for formulation development rather than universal recommendations.
Application Testing Remains Essential
Technical data sheet viscosity values provide an important reference, but the final ink must be evaluated under actual formulation and printing conditions. The behavior of a resin at its listed viscosity does not necessarily predict the viscosity, jetting stability, curing response, or print quality of the complete ink.
For this reason, resin selection should be followed by formulation trials using the intended pigment system, monomer package, photoinitiator, printhead, curing equipment, and substrate.
Lencolo's UV material portfolio provides low-viscosity resin candidates across polyurethane acrylate and epoxy acrylate chemistries, allowing formulators to compare different approaches according to their specific UV inkjet requirements. The objective is not simply to achieve the lowest possible viscosity, but to establish a stable formulation that combines suitable jetting behavior with the curing, adhesion, flexibility, and durability required in the finished print.
https://www.lencolo37.com/
Guangdong Lencolo New Material Co., Ltd.
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