From what Dead Link Removed, DVDs are read with a wavelength of 780nm (Red light/infrared light barely within visible spectrum). UV is actually on the entirely opposite end of the spectrum. Normal DVD's are pressed to create different indention in the plastic that cause the reflectivity of the laser to differ. Recordable DVDs have a dye layer that is heated to make pits that react the same way as a pressed disc. So its not really UV light, but heat. I suppose for recording, the wavelength doesn't matter as long as the heat is correct. The webiste says that recording lasers often peak at 200mW.
I'd say you could not just put a DVD behind a pinhole and get an exposure, no matter how long. I mean, DVDs don't go bad if you leave them in light. Also, since the dye on recordable DVDs is manipulated by heat, contact printing the negative would probably melt the negative first.