What is the film on the back part of the screen assembly?

Replacing Iphone 6s Battery

• Noticed a small nick/tear on the rear screen assembly film.
• What is the purpose of this film, and will it cause any issues if there is a nick/tear in it?
• Should this be patched with something that is not electrically conductive, or just left alone?
• The display assembly is stock and here is a picture with the nick/tear in the film

• Hear is a larger image for the assembly taken from a stock photo on IFIXIT and an arrow pointed at the part i'm referring too