HP is suing the German subsidiary of a Korean company for violating its printer ink patents.

The company has filed a formal complaint in Germany alleging that InkTec, and its branded "do-it-yourself" cartridge refill kits violate HP patents. Even though InkTec is in South Korea, HP filed the complaint in Germany because it had found the ink cartridges in the country.

HP said the discovery of the infringing InkTec products is the result of ongoing testing and enforcement efforts within the Supplies unit of HP's Imaging and Printing Group. Over the past year, the same approach has fought ink patent infringements by other companies that offer generic ink supplies through refilling stations or "private label" brands.

Both its inks and ink cartridges are highly engineered and protected by multiple patents, HP said. They are the highest margin products sold by HP, which also sells desktop and notebook computers, servers and storage technology, printers and other products. A recent blog posting pointed out that HP ink now cost nearly double human blood, per millilitre, and is nearly 50 times more expensive than vodka.

Because replacement cartridges cost $30 or more apiece, numerous businesses have sprung up in recent years to refill existing cartridges for sometimes half the price of a new cartridge. InkTec is a provider of inks, remanufactured cartridges and cartridge refill kits whose stock trades on the Korean stock exchange.

Original reporting by IDG News Service