A US firm has indicated it feels Apple may have infringed yet another of its patents. Quantum Research (QR) says it may file a case against Apple for the touch technology used in the iPhone.

It has previously launched a legal challenge to Apple's use of the iPod click wheel on the iPod nano. The player uses 'charge transfer' technology that, QR says, belongs to it.

Duncan Bryan, licensing director at Quantum Research , told Electronics Weekly : "We will be looking very carefully at the iPhone. The description of the iPhone suggests it uses a rear-surface touch screen, and has proximity sensing which can tell if it is held to the ear."

Bryan indicated such a screen was a "QR capability".

On its website, QR says it "is the leading touch supplier for today's human interfaces".