I recently installed ubuntu 16 on a dual boot with windows 8 on my lenovo g50-80. After completing the ubuntu installation and booting back to windows it shows a patchy screen as shown in the image.
If it only happens after rebooting from Ubuntu, then it's just the remains of what was in the video card's memory being displayed in Ubuntu before Windows boots up. There's no real point in clearing out the video RAM when the OS is starting because everything is going to be overwritten when the desktop is displayed. Clearing out the RAM would take extra time, and slow startup times can make some people impatient. When the computer first boots up, everything should, (theoretically), be cleared out already, which is why you only see black screens when starting the OS. If you restart the OS and load another one, there could still be things in the video RAM, and you might see portions of it. The reason it looks like junk is that the OSs are using different areas, sizes, and image formats for their display areas.