Heating it with electric hair drier can make it easy to tear it off.
Cover the film with warm towel for a while. It will be easy to tear it off.
You can give electric hair drier a try. Try put the drier 15cm away the film and heat the cornor at first. If you find it easy to tear off, you can exend the area. Note: do NOT blow the main part of the film for too long.
