Anti Reflective Coatings
For the coating process, we use Ion Assisted Vacuum Deposition (IAD) technique. For the cold evaporator method, the general control temperature is about 80deg, but for the thermal evaporator method, the general control temperature is about 250deg. We use the Cold evaporator method since Jan 2017 for fear of chrome removal through high temperature.
Coating Types:
- HfO2 for single wavelengths > 220nm
- SiO2 for single wavelengths > 350nm
- Ta2O5 & SiO2 multilayered coatings for wavelengths > 350nm
- HfO2 & SiO2 multilayered coatings for wavelengths > 220nm. Please note this coating may have slight cosmetic defects such as pitting when applied.
Specs with UV wavelength can only be applied with HfO2, as HfO2 has absorption only under 220nm. The disadvantage of HfO2: the coating material is easy to create digs and spatters. So, below 350nm, then HFO2 must be used but above that then Ta205 because the surface quality is better. The advantage of Ta2O5: It has absorption under 350nm, which is available to the general coating recipe above 350nm. Ta2O5 is a kind of regular coating material. There is no surface quality issue on the general coating recipe with it.
What chemicals can be used to clean?
The mixture of ether and absolute ethyl alcohol.
Submersed time less than 12 hours. If it is more than 12 hours, it may affect the AR coating removed. You can clean (wipe, no bath) the parts with IPA and Acetone for a short time
Thickness of coating
200-400nm generally
Hardness
1. Degree of severity (Conditional Method: Abrasion)
No damage using method 1, Abrasion EG, Wipe 40 times with eraser and 1 kilogram-force, there’s no scratch
2. Degree of severity (Conditional Method: Adhesion)
Note: The "snap" rate of removal refers to a snapping action of the wrist and fingers
No coating removed using method 2 - adhesion
