hardcoatings Hardcoatings are thin films which are deposited on tool substrates in order to improve their desired properties such as hardness, friction, wear resistance, and corrosion resistance, while not changing properties of the bulk material. Scratch resistant coating or hard coating provide lenses with durability and increased longevity. A high quality thermally cured hard coat provides the best scratch resistance and provides for the most durable ingredient for an AR coating application. Plastic lens materials scratch easily than glass materials, and therefore benefit greatly with application of a durable hard coat.

Two of the more common types of hard coats are: Thermally cured hard coating The lens is slowly passed through a liquid bath of a solvent based hardcoat where the coating solution adheres to both convex and concave sides of the lens. The hardcoat is then allowed to cure in a high temperature oven until stable. U.V. cured hard coating A liquid hardcoat solution is applied to the concave side (backside) of the lens using a spinning process. Lenses are then cured under a UV (Ultra Violet) light for a specific amount of time.

Soft and Hard coating Traditional, soft coatings, a technique commonly used for coating optical components, may soon be rendered obsolete by a higher performing coating technique known as hard coating. As detailed, hard coatings provide several advantages to traditional soft coatings. Soft Coatings Soft coatings are multilayer thin films consisting of zinc sulfide, cryolite, and, sometimes, silver. For traditional interference filters, the coated components are laminated together in a vertical stack to provide some protection from the environment and, typically, cored from a larger wafer. Because of the materials and manufacturing process used, soft coatings are fragile. The coating material is often removed from the edges of the filter in order to avoid degradation caused by moisture and to increase the coating’s lifetime. The cost of soft coatings is maintained by the low cost of the deposition equipment, fast cycle times, and inexpensive float glass substrates.

Hard Coatings Hard coated films are developed using a plasma deposition process that provides multiple benefits compared to soft coatings. The plasma deposition process is tightly controlled using a computer, which allows for even layering, high environmental aptitude, and improved performance. For instance, not only is the transmittance of a hard coating more consistent as a function of wavelength, but it is also generally superior to the transmittance of a soft coating. hard coatings can provide over 90% transmission throughout the visible spectrum and into the UV. On the other hand, soft coatings cannot achieve 90% transmission and face significant performance declines near the UV. Soft coatings have a gradual change from no transmittance to maximum transmittance, while hard coatings achieve much steeper transition.