For a slightly aviation related project I am playing with some ITO coated glass.
It is 50-80% transparent, according to the thickness of the coating. One can get it with various resistances; the ones I have are 40 ohms per square.
This stuff is perfect for heated windows.
I read somewhere that some airliners use ITO coated windows…
I didn’t know ITO was also used as heater. I knew about and experimented with ITO coating for EMC screening of monitors. While investigating lots of MIL-SPEC monitors have this coating to prevent one reading the display trough the RF generated by the screen. Interesting technology.
However for lower resistance, which is required for proper heating the opacity goes down.
Also the coupling between coating and busbar can be difficult, though I would guess for heating this would be a lot easier then for RF / EMC purposes.
Then one manufacturer informed me that it will discolor and become brown, and the opacity will be reduced over time.
This piece measures at about 5 ohms per square, which is very low.
Re corrosion resistance, one might have to coat it, or laminate it with the coated side against another layer (with adhesive).
Peter wrote:
This piece measures at about 5 ohms per square, which is very low.
That looks much better then the 40 ohms square as you indicated before.
Peter wrote:
or laminate it with the coated side against another layer (with adhesive).
I think this is the standard method with displays. I didn’t speak about corrosion, for RF applications they use an gasket to have proper contact all around. I think something similair would be needed if you want to keep it at low resistance for heating. When you would just lay it flat on aluminium, you would have just some points of contact, no proper contact over the whole length.
Another issue I had, that allthough it was anti glare, I found it still to much glare to satisfy my needs.
The 40 ohm was specced with 80% transmissivity. This one is about 50%.
For anti reflection one needs specific coatings.
Peter wrote:
For anti reflection one needs specific coatings.
Sure, the samples I used had this anti reflecting coating, but I think they still reflected far to much, for my liking. I was looking for a matte display.
I am working for a leading avionics display manufacturor. We are using ITO coatings both as a shielding and/or a heating element in the optical stack of our displays. We can also offer mesh filters as EMI shielding. It all depends on the exact requirements and budget.
That’s really interesting, @Niner_Mike
I have started a more specific thread here
To answer the original question: My guess would be certification/approvals issues.
