Blank Discs are one of the components required for the Disc Developer. In order to create a game disc you must first acquire a Blank Disc along with Idea Chips. They make their first appearance in Hyperdimension Neptunia Victory.
There are a number of different Blank Discs and each have their own Idea Chip Category and Level combinations which will determine the type and level of the Idea Chips you are able to use for that particular Blank Disc. Black Discs are generally rewarded for obtaining Large Medals, but may also be granted through Chirper events or other means.