Can't find anything particularly scholarly specifically about the effects of a blacklight on reptiles, but it seems to be fairly agreed-upon knowledge that BLB lights are unsafe for reptiles -- including BPs.

The issue with a BLB bulb (This goes for humans and animals alike, though humans generally have a higher resistance) is that the wavelengths is short enough that it doesn't cause the pupils to contract, and therefore can essentially burn out the eyes over an extended period of time. The reason that full spectrum lights don't have a similar problem is that they're just that -- full spectrum. The full spectrum of light DOES cause the pupils to react, and has little chance of harming the eyes.

Now, a BL tube is supposedly safe -- but keep in mind that a BL tube isn't going to produce the same effect as a BLB poster light, but will rather look more like the light of a bug zapper (Which uses the same type of technology). This means that it will be fairly bright, and will be a blue-white colour. An incandescent BL tube should have no purple/black filter like a BLB bulb will, so if you still decide to go that route, be careful what you buy because a lot of places don't expect people to know the difference and the labeling can get mixed up.

Also do keep in mind that BL tubes generally get VERY hot, and that could mess with your temperature readings and could dry out your tank if you aren't careful.

Hope I could help!