Yes, this includes ultraviolet light.

Why? Does it also include x-rays? That’s only one step further on the electromagnetic spectrum. Seems arbitrary to stop at ultraviolet waves! Does that mean thin sheets of steel aren’t opaque? Or is it the term “opaque”, without any modifiers attached, colloquially used to describe whether something permits visible light through?

For the record, they’re not opaque. The article actually says they work better if you close your eyes.