Sony has sued US photography giant Eastman Kodak in a US court for breach of 10 patent rights relating to digital cameras.
Kodak and Sony are battling for digital sales
Sony's lawsuit ratchets up the tension between the two, coming three weeks after Kodak filed a similar case against the Japanese firm.
However, Sony has denied that its lawsuit is a tit-for-tat move, saying it relates to different patents.
The spate of lawsuits between the two follows protracted talks.
The 10 patents at the heart of Sony's case "make the handling of digital images easier, and they also make the system control for handling digital images easier still," a spokesman for the Japanese firm said.
A Kodak spokesman, Gerard Meuchner, has refused to comment, saying he had not seen the details of Sony's lawsuit.
On 9 March, Kodak sued Sony for patent infringements, also citing 10 patents used to develop digital camera technology.
Kodak said that those patents dealt with "electronic camera utilizing image compression and digital storage".
The popularity of digital cameras has hurt profits at Kodak, which is the world's biggest maker of film and was a pioneer of use of photographic film a century ago.
Digital cameras do not require film, using a computer chip to store the images instead.
Both Kodak and Sony have moved into the digital camera market, where Sony has seized one-fifth of worldwide sales.
When Kodak filed its lawsuit, Mr Meuchner said the two companies had been in talks over a suitable licensing agreement for "almost three years", but had failed to agree.