A monitor driver is not essential like it is for a GPU or sound-card, since the monitor will work properly without one, and indeed many PC users simply leave it as the default "Plug and Play Monitor" in Device Manager, whilst some monitor manufacturer's don't even bother releasing drivers for some consumer-priced models.
I've checked the downloads for that model on BenQ's US website & they don't have a driver for it, only a Data Sheet & and the User Manual.