IMAGE: BRYAN CHRISTIE

FUJITSU 183: In the three-electrode, surface-discharge reflection structure covered by Fujitsu's Patent No. 2845183, address electrodes run under and parallel with alternating red, green, and blue phosphor channels, while pairs of transparent display discharge-sustain electrodes embedded in a transparent front substrate run at right angles across the channels. A voltage is applied to pairs of selected display electrodes on the grid, prompting gas to discharge and emit ultraviolet light, which causes the phosphor to emit visible light.

Editor's note: This story is an updated version of the report that appeared in the June print issue of IEEE Spectrum.

On 7 June, consumer electronics firms Fujitsu Ltd. of Japan and Samsung SDI Co. Ltd. of South Korea, announced that they have ended a bitter patent dispute over the technology behind their plasma displays. Both companies have dropped lawsuits filed in the United States and Japan, and Fujitsu has withdrawn its request that its rival be barred from selling its products in Japan. The battle started in February, when Samsung filed a lawsuit in the United States challenging the validity of Fujitsu's patents. Fujitsu, which was a pioneer in the plasma display technology, countersued, claiming that Samsung had violated its patents. This kicked off a flurry of suits and counterclaims.

On 21 April, Japan's customs authorities imposed a temporary import ban on PDPs manufactured by Samsung. Meanwhile, in Seoul, Lee Hee-beom, South Korea's Commerce, Industry, and Energy Minister, summoned the Japanese ambassador to a meeting and demanded that Japan's customs authorities halt their “unilateral” action.

This series of tit-for-tat moves followed an earlier flurry of lawsuits by both companies and represented a distinct escalation in hostilities. Though Fujitsu has a reputation, unusual in Japan, for U.S.-style litigiousness, in this case Samsung fired the first shot. Fujitsu had filed suit against Samsung on 7 April in Federal District Court in Los Angeles and against Samsung Japan in Tokyo District Court, alleging infringements of its PDP patents. But that action came after Samsung had earlier filed its own lawsuit in the same Los Angeles court used by Fujitsu, disputing Fujitsu's patent claims.

Fujitsu invented the PDP in the 1970s and has built a portfolio of over 800 patents to protect its intellectual property. Its suit filed in Tokyo concerns Japanese Patent No. 2845183 (dubbed 183), which covers one of Fujitsu's most fundamental PDP patents, the basic structure of the plasma discharge operation.

A PDP is made up of two glass substrates enclosing a discharge gas, which can be a mixture of neon and xenon, for example, and a crisscrossing grid of discharge and address electrodes. The address electrodes run under and parallel with ribbed channels coated with red, blue, or green phosphor, while pairs of discharge-sustain electrodes cross the phosphor channels at right angles. Voltage is applied to a pair of discharge electrodes and an address electrode at a selected intersection on the grid. The voltage between the top and bottom electrodes prompts the encased gas to discharge and emit ultraviolet light, which causes the phosphor to emit visible light.

This design, which uses a transparent upper glass substrate and transparent display electrodes, is known as the three-electrode surface discharge reflection structure and is covered by Fujitsu's patent 183. It improves on earlier Fujitsu designs that used pairs of electrodes facing each other, one on each glass substrate, which prompted a discharge through the phosphor, damaging it; another design had the visible light produced pass through the phosphor, reducing brightness.

“This 183 Japanese patent is one of the most fundamental [PDP] patents,” Masanobu Katoh, president of Fujitsu's Intellectual Property Group, told IEEE Spectrum in Tokyo. “And in our understanding, everybody who manufactures plasma displays in the world uses this technology.”

Katoh says Fujitsu has contracts with PDP manufacturers Matsushita Electric Industrial Co., in Osaka, and Pioneer Corp., in Tokyo, concerning its PDP intellectual property, and is holding negotiations with LG Electronics Inc. in Seoul. He adds that it was when talks broke down with Samsung after two years of negotiations that Fujitsu turned to the courts.

Driven by growing worldwide consumer interest in large TVs, twice as many PDPs—1.78 million units—were shipped in 2003 as in the previous year, according to market researcher DisplaySearch, in Austin, Texas. Fujitsu Hitachi Plasma Display Ltd. (FHP) ranked first, with a 24 percent market share, followed by Samsung, with 20 percent, a dramatic rise from Samsung's sixth-place 2002 rank.