APPLICATIONS
Metallizing
Metallizing is the process of depositing a thin reflective layer onto the embossed micro-structured film surface. This reflective coating is what transforms the invisible microscopic grooves into brilliant optical effects visible to the human eye. Without metallization, the embossed micro-structures would produce only weak, barely perceptible optical effects.
Vacuum Aluminum and Transparent Dielectric Coating
The most common metallizing process is vacuum evaporation of aluminum. The embossed film is loaded into a vacuum chamber from which air is evacuated to create a high-vacuum environment. Aluminum wire is heated to approximately 1,093 degrees Celsius (2,000 degrees Fahrenheit), causing it to vaporize. The vaporized aluminum atoms travel in straight lines through the vacuum chamber and condense onto the embossed film surface, forming a continuous reflective layer typically 30 to 50 nanometers thick. This aluminum coating provides a highly reflective mirror surface that follows the exact topography of the embossed micro-structures.
When light strikes the metallized micro-structured surface, the aluminum layer reflects the light while the microscopic grooves diffract it into various directions. The interference between light waves diffracted from adjacent groove structures produces the characteristic optical effects: spectral color separation, apparent depth, motion, and other visual phenomena. The precise groove geometry determines which wavelengths are reinforced in which directions, creating the specific optical effects designed in Holoshop.
In addition to aluminum, ROEM can deposit transparent dielectric materials such as zinc sulfide (ZnS) and silicon dioxide (SiO2). These transparent coatings create different optical effects compared to metallic aluminum. Zinc sulfide, with its high refractive index, produces interference-based color effects (similar to oil-on-water iridescence) that change with viewing angle. Silicon dioxide can be used as a protective overcoat or as part of multi-layer dielectric stacks that create specific spectral filtering effects. Transparent coatings are particularly valuable for applications where the holographic effect must be visible over printed backgrounds or where see-through properties are desired.
After metallizing, the film may receive a protective lacquer topcoat to prevent oxidation of the aluminum layer and to provide a surface suitable for subsequent printing or adhesive application. The roll of metallized film, which may be up to 2.3 meters wide in industrial production, is then prepared for the final lamination stage.
