What type of glue is used on the front LCD Polarising film?

This is not a repair question as I have no intention of putting anything back, so it's more of an in-depth tear down one...

I'm trying to cleanly extract a specific layer of the LCD module including removing the polarising film. I've done this on other types of screen, mainly LG monitors and the polarisers have come away easily.

After removing the front glass with a heat gun and some wire I've managed to get the glass layer I want out and removed the polarising film already but the glue on this 5c's LCD is stubborn, so far it's not been touched by acetone, contact cleaner or WD40. It will come away with a blade eventually buts its painstakingly slow going. Anyone know what this stuff is and how I can remove it?