there is disclosed a portable thermal printer having a printer housing , a printing mechanism and an ink ribbon cartridge containing an ink ribbon cartridge containing an ink ribbon . the cartridge has a cartridge housing and an improved brake for applying a slight braking force on a core of an ink ribbon supply roll in the housing . the cartridge is easy to load onto the printer . the cartridge forms part of the printer housing and is latched thereto . the cartridge is slid onto the printer and the cartridge housing detents into position .