Acer has filed a patent counterclaim in the US against rival HP as part of its response to two HP lawsuits.

The lawsuits come amid a major push by Acer into the U.S. PC market, and brisk global growth. The Taiwanese company's shipments to the US, HP's home turf, grew 163.8 per cent year-on-year in the most recent second quarter, according to preliminary figures by market researcher IDC. HP has also been gaining market share in PCs at the expense of other rivals such as Dell, but Acer remains the fastest-growing PC maker among the top 10.

The counterclaim filed last week by Acer alleges HP has infringed its antenna and DVD-ROM head technology patents. The suit was filed in the same court as the HP lawsuits against Acer, the US District Court for the Eastern District of Texas.

The HP lawsuits claim that Acer has infringed 10 HP patents related to PCs. The world's largest PC vendor is seeking to block Acer PC imports to the U.S. and is asking for compensation from Acer, payment of legal fees, and triple damages for alleged intentional violation of the patents.

Court documents in the Acer counterclaim were not yet available at the time of writing.

Acer has said it believes its contracts with contract PC makers indemnify it from HP's claims, and has already filed a lawsuit against three of its suppliers aimed at forcing them to live up to their contracts. Many laptop and desktop PC suppliers do the design and manufacturing work for customers. Acer said that since its suppliers worked on the design of the PCs in question, they should share the burden of the HP lawsuit. The supplier agreements specifically indemnify the company from lawsuits such as the two brought about by HP, Acer said.

The HP lawsuits come as Acer continues to gain market share in the global PC business, and some analysts have called the disputes a response to the inroads Acer has made in the U.S. PC market.

Acer's shipments to the US grew 163.8 per cent year-on-year in the second quarter, according to preliminary figures from market researcher IDC, beating all other companies among the top six. The Taiwanese company more than doubled its market share to 5.2 per cent from 2.1 per cent a year ago.

"Acer continued its rapid expansion in the Americas while posting strong gains in other regions as well," IDC said in a statement. New retail and dealer partner agreements are boosting Acer's drive into the US market, the industry researcher said.

By contrast, HP's shipments in the US grew 26 per cent over the same time. HP retained its title as the world's biggest PC vendor with a 19.3 per cent share of the market, compared to 7.2 per cent for fourth place Acer. Acer's worldwide shipments in the second quarter rose 55 per cent against the same time last year, compared to 36.5 per cent growth for HP.