UV light transparency is crucial for ensuring effective UV curing. Without sufficient transparency, UV resins or matte coatings and inks will not exhibit proper photoactivity, making them unsuitable for applications that require UV curing. This requirement is especially important in LED curing processes.
Matte UV Formulations Must Avoid Wax Pastes and Silicones
The amount of matte agent added to a UV formula must be strictly controlled. Excessive amounts do not just lead to thickening issues. There is a threshold for the matte agent in UV formulations, typically around 10-15%. Beyond this point, it acts only as a filler, contributing to thickening without enhancing the matte effect. Overuse can lead to poor dispersion, causing issues like poor scratch resistance, powdering, white spots, and softening after curing. These factors also negatively impact hardness, abrasion resistance, and chemical and water resistance.
Moreover, simply adding a matte agent results in a semi-matte product and is heavily influenced by the substrate’s gloss level. For example, adding a matte agent usually only reduces gloss by half of the original substrate’s gloss. Adding wax pastes or silicones can lead to even more severe problems, such as surface oiling, poor curing, softness, lack of recoatability, and the inability to apply hot stamping. Thus, wax pastes and silicones should be strictly avoided in matte UV formulations.
Matte UV Formulations Require Pigments and Fillers That Contribute to Synergistic Matting
The matting effect in UV formulations still relies on the diffuse reflection mechanism of matte agents. However, UV curing requires high transparency, leading to excess transmitted and reflected light. Traditional matte formulations lack sufficient components to absorb this light, so the design principles for UV matte products are different.
The formulation must consider the resin’s high photoactivity, ensuring deep and thorough curing. Additionally, it is essential to include sufficient light-absorbing components to reduce reflectivity while maintaining transparency for effective curing. Fillers and pigments must be chosen carefully for their dispersion, stability, anti-settling properties, light transmittance, and light absorption capabilities, all while working synergistically to enhance the matting effect.
Current tests show that fillers below 3000 mesh hinder UV transparency and curing, while fillers above 6000 mesh exhibit good transparency. However, some fillers may cause whitening in liquid form, so the selection of materials must balance transparency and matting effectiveness.
Post time: Sep-16-2024
