Tech Watch: Proell’s Norilux® DCAL Screen Printing Lacquer

The Norilux® DCAL screen printing lacquer has been developed for decorating and protecting automotive door sills, design trim elements, loudspeaker grilles and center consoles made of aluminum or stainless steel. Norilux® DCAL is formable on applicable substrates and highly abrasion and chemical resistant, which can be used as a first surface protective lacquer or hard coat. The cured layers also pass various cream tests of the automotive industry.

This protective lacquer can be used for overprinting siliconefree UV solvent and water-based screen printing inks including the Proell ink systems NoriScreen® ALU and NoriPUR® to protect the printed ink layers.

“Dual cure lacquers for decorating and protecting metals are new,” said Dr. Sven Koenig, manager UV curing screen inks & dual-cure lacquers, Proell. “After UV curing of the lacquer layers, the mechanical and chemical resistances of the decorated parts are significantly higher compared to those printed with conventional screen printing lacquers.“

Additional potential applications include automotive design trims, center stacks as well as faceplates for household appliances made of metals. Norilux® DCAL is available in a matte version as well as varying gloss levels, tints, and effect lacquers such as a sparkling effect upon request.

Primer pre-print
When choosing to print a primer layer, such as any color shade of NoriScreen® ALU or NoriPUR®, the dried ink and/ or lacquer layers can be overprinted with Norilux® DCAL. When overprinting lacquer or ink, Norilux® DCAL must be processed as a two-component system with Hardener 036.

Direct print
Norilux® DCAL protective lacquer can also be printed directly onto a metal substrate without a pre-printed primer. Adding 10% adhesion promoter NoriCure® HV-M to the homogenized Norilux® DCAL/ Hardener 036 mixture is necessary when direct printing.

Drying / conditioning
The dual cure system Norilux® DCAL dries first by evaporation of solvents in jet dryers. Before UV curing, printed Norilux® DCAL layers cannot be stacked. As a result, the uncured substrates should be stored separately in a rack after jet drying.

Before further processing (forming, trimming), the printed substrates must be dried at 80 °C to 100 °C (176 °F to 212 °F) for 30 minutes. Minimizing solvent residues is necessary for dual-cure lacquer Norilux® DCAL to achieve its outstanding properties.

Forming or bending process
The decorated metal substrates can now be formed by high pressure forming (in case of thinner aluminum substrates), thermoforming or cold forming. For deeper forming geometries, thicker lacquer layers are required. Those layers can be achieved by using coarser screen fabrics such as 90-40 threads/cm (230-40 threads/inch).

UV curing
For UV curing of Norilux® DCAL lacquer layers, highoutput mercury bulbs with > 120 W/cm (300 W/inch) are required to achieve best resistances.

After UV curing, the cured substrates can be further processed by diecutting, trimming or mounting.

“The dual cure lacquer is already in serial production for automotive door sills and design trims in Europe, the United States, Mexico and China,” Koenig said.

The Norilux® DCAL lacquer offers many benefits, including decorated metal plates that are better protected for their final application. Koenig said there are fewer restrictions for the use of cleaning agents (detergents) due to the excellent chemical resistance of the finished design trims (automotive sector) or faceplates (household appliances).