Polymer Optics on the Rise
Polymers have recently become a more popular choice for consideration when designing optics, and have many advantages: weight, cost to produce, impact resistance and manufacturing time to name a few. However, they are not without inherent limitations, including poor chemical resistance and subjectivity to scratching and abrasion problems. In use, plastic optics are subject to regular cleaning which can damage an uncoated part and any subsequent coatings applied directly to the bare substrate. The use of solvents and standard household cleaners can quickly begin to effect the coating or optic and cause premature failures once the part is commissioned for use.
To increase the durability of these substrates, NACL has several options to mitigate these issues with our dip-applied hardcoating as well as our vacuum process. Whenever possible, we recommend the dip-applied hardcoating due to its overall durability being superior to that of the vacuum applied process. Sometimes the dip process does not lend itself suitable to the project or substrate due to sophisticated geometries or surface quality requirements. Additionally, the dip process requires thermal curing so if the part has temperature restrictions or is very thin and fragile then the VHC – 2000A is a better choice.
VHC – 2000A
NACL has several systems capable of applying the VHC – 2000A and each is set up to best accommodate the size and shape of the substrate. With our years of experience encompassing a wide range of plastics and polymer optics, we have created a library of formulations to ensure proper adhesion and optimal durability. The VHC – 2000A is a good base coating choice for any additional optical coatings applied to the polymer substrate, such as: anti-reflection coatings, ITO (indium-tin-oxide) coatings, beamsplitters, bandpass filters and many more.
People often ask if we can apply the hardcoating on top of the optical performance coating to make it more durable. The problem is that the optical coating is using multiple layers on dielectric materials with varrying indices of refraction. These layers are put on in exact thicknesses in a very specific order to manipulate light waves in accordance with the required specifications. Optical coatings need to be at the air interface (or matching substrate) to perform properly. Adding the hardcoating on top of the optical coating negates the effectiveness of the optical coating, rendering it useless.
The typical thought process suggests that the hardcoating underneath the optical coating will not be effective. A simple analogy to provide some clarity can be likened to putting an extremely thin sheet of glass on a pillow. If we imagine the glass sheet being the performance optical coating, the pillow being the polymer substrate and we then poke our finger into the center of the glass it will break through the “optical coating.” However, if we put a sheet of plywood (the hardcoating) underneath the glass and again attempt to poke through the glass, it will now withstand the force and remain unaffected.
In any case, when working with any plastic or polymer optics, we recommend considering one of the hardcoating options to enhance the performance of the part in its final form.
Individual data results vary by the polymer type, so if you are interested in additional details, please feel free to reach us via email at firstname.lastname@example.org or call 866-216-6225 for more information.