1st post yeah !

Hi all.
I have a bit of a problem on my Volvo C30 Windscreen.
I have been away for 3 weeks and my car stood on the sun and when I got back a had this "blue waterdrop" tint/film all over the outskirts of the wiper blades reach.
Now I can't wash it off. I been told by a lad from a car wash, that it is some kind of oily/greasy residue that was burned onto the glass by the sun and I need some kind of scraper/scratcher to get it off.
I am trying to find it, but no luck.
Did anyone deal with this kind of problem or does know what I need to get rid of it?
Thanks.