Apple ramped its legal battle with Qualcomm by calling for four patents held by the chip technology giant to be invalidated.

The iPhone maker’s submission to the US Patent and Trademark Office is the latest salvo in a wide-ranging spat between the two, which covers multiple regulators and territories.

Bloomberg reports Apple wants the Qualcomm patents invalidated because they do not cover new ideas. The intellectual property involved is cited in a Qualcomm case against Apple filled in California during 2017, which would obviously be undermined if the Cupertino company’s petition is successful.

The patents relate to topics including autofocus on digital cameras; devices which function as both phones and PDAs; touch-sensitive displays; and memory.

Bloomberg said Apple is “one of the most aggressive users of the Patent Trial and Appeal Board”, stating it offers “easier” legal standards than the courts.

Earlier this week, Reuters reported Qualcomm had picked up a boost from the US International Trade Commission in the form of a finding Apple had violated a patent related to battery power saving (which does not appear to be on the current list).

The dispute kicked off in anger in January 2017 when Apple accused Qualcomm of unfair licensing practices: its royalties are based on device sale price, regardless of how much Qualcomm technology is inside.

Qualcomm responded by stating Apple “intentionally mischaracterised our agreements and negotiations” and was withholding royalties.