Moxtek’s inorganic wire grid polarizers provide outstanding performance and high heat resistance in the UV, VIS and IR from 240 nm to 15 µm. However, the wire grid structures have a 100 nm pitch and can easily be damaged by touch or during cleaning.
This is why Moxtek has now developed a protective wire grid coating. This coating gives mechanical support to the structure and allows for (careful) wiping and cleaning. It is thermally stable for temperatures up to 300 °C (1000 hours) and barely effects the polarizer’s performance. Abrasion behavior, adhesion and chemical resistance were thoroughly tested.
For these tests, the polarizers were “rubbed” with different tools. The tests were performed in accordance with military standard MIL-C-48497 which establishes pressure and friction angle. Moxtek used a semi-abrasive scrubber, brushes, cotton swabs and various cloths for the tests.
To test adhesion, transparent tape was applied to the wire grid surfaces of two polarizers – one with and one without protective coating. After the tape was removed, the coated polarizer did not show any damages and was fully operational, whereas the polarizer without protective coating showed considerable damage. This polarizer could not be used any more.
To determine the chemical resistance, different solvents like methanol, acetone and isopropyl were applied to the coated side of the wire grid and were left to dry overnight at room temperature. The optical performance was measured before and after the tests. Again, no negative impact was detected.
Uncoated polarizers cannot be cleaned, as this will destroy the wire grid structure so they cannot reach their specified performance any longer. A newly developed coating protects polarizers from damage caused by contact and makes careful cleaning possible.
Despite these new possibilities, it is still a good idea to wear gloves when handling coated polarizers to protect them from fingerprints and contamination.