UV-imprinting

UV-imprinting is a versatile technology to manufacture structured and optical products for a broad range of applications. Pioneered in the 1980's and originally applied to manufacture early optical data storage products and later on also CD, DVD, and BluRay discs, it has shown to be able to supply solutions for markets where plastic injection molding fails to deliver the desired quality. Being a 'cold' technology, higher accuracies in shape and alignment can be reached compared to processing at elevated temperatures.

In UV-imprinting applications, a resin consisting of monomeric units and a photochemically active compound is applied to the targeted substrate or mold that is equipped with the designed shape/structure/texture. Next, the resin is spread by the process to fill up all these patterns in the mold.

Subsequently, UV light is cast at the resin through mold or substrate which initiates the polymerization reaction of the monomeric units and finally a polymer mirror image of the mold pattern is produced. This so-called family process can be used in a similar way to again end up with an exact copy of the mold pattern. It has to be taken into mind that resin shrinkage occurs during polymerization, but careful design can easily overcome this.

A typical UV-imprinting process consists of the following steps:

Substrate pretreatment. In most cases the substrate has to undergo a process-specific treatment to improve the adhesion of the UV-curable resin to its surface. Many types of substrates are suitable, including metal, plastic, glass, and quartz. In principle, when the proper adhesion promoters are used for a specific UV-curable resin, then any substrate material can be used.
Resin application. There are a number of ways to apply UV-curable resin to a substrate. The most appropriate way depends on application, substrate size, and lacquer rheology. Examples of resin application include puddle dispensing, spin coating, doctor blade application, and others.
Contacting. By closing the gap between mold and substrate with applied resin at some point contact is made through the resin and, subsequently, the resin can be carefully pressed out.
UV-curing. Using a UV-light source, photo polymerization is initiated which results in curing of the resin. When required, mold and substrate can be accurately aligned prior to UV-curing.
Product release. After the resin is fully cured, product and mold are separated from one another. The mold can be reused again for another UV-imprint.