LG's Zenith goes after Sony in patent trouble - Wikimedia

An LG subsidiary, Zenith Electronics, has it in for Sony in the latest patent mix-up.

Two claims relate to Sony's Bravia HD TVs, which are allegedly in breach of Zenith patents. Funnily enough the claims come just days after a federal judge in Texas granted Sony's bid to move a separate patent suit against Zenith.

Tit for tat, Tweedledum and Tweedledee. Zenith says Sony's HDTV and receiver products that implement the Advanced Television Systems Committe standard are in breach of its patents.

In a bid to show it has a case, Zenith has cited Sony's KDL-46HX800 and KDL-32EX500  models as infringing patent numbers 5,565,932 and 5,406,587  and is seeking enhanced damages.

The two new claims now bring the number of complaints to 12.

Zenith said in a statement: "While Sony Corp. was previously licensed to certain Zenith patents, that license has expired and Sony's sales of HDTVs have been and continue to be unlicensed sales in violation of Zenith’s patent rights.

"Zenith has contacted and attempted to negotiate a reasonable and nondiscriminatory license with Sony; however, Sony has been unwilling to take a license to Zenith’s patents."

It added that Sony had made, offered to sell or sold, and/or imported into the U.S. ATSC-standard compliant HDTV products that infringed the two patents in the  suit.

There are already three ongoing ITC investigations between the pair.

Two of those investigations are down to complaints lodged by Sony, while the third looks into two LG complaints, one already over the Bravia TV sets and one over the PS3. 

The PS3 complaint caused a great deal of media attention when LG managed to get a court order to ban imports of the console. Allegations were based around the Blu-ray Disc player.
 
According to IP expert Florian Mueller, if the latest complaint by Zenith is taken seriously then the ITC will begin a fourth investigation.

So far, the squabbling pair have brought over a dozen complaints against each other and asserted a total of 50 US patents. There are 31 from LG including its Zenith Electronics subsidiary, and 19 from Sony - plus the European counterparts of some of those.