PDM / PDMagnetics - PD Magnetics was founded shortly after Dupont invented chromium dioxide tape in 1970, and Philips joined in developing this improved tape. PD stands for Philips and Dupont. Philips then focused on its own brand. And Japanese brands like TDK and Maxell, unwilling to pay royalties to Dupont, developed and manufactured their own. PD Magnetics continued to manufacture tapes into the 1990s, but failed to capture significant market share.