The companies already, in South Korea to produce the panels.
The expansion allows Samsung, the world's second-biggest maker of large-size liquid crystal displays last year, to use Sony's brand power to expand the market for .
Analysts also have been expecting Sony, Japan's second-largest consumer electronics maker after Matsushita Electric Industrial Co., to invest in new production capacity to secure panels for its new , which have made big strides in grabbing market share in the United States and Japan.
Panel supply was a key reason behind Sony's rise to the top spot in LCD TVs in the fourth quarter of 2005.
"Samsung and Sony have seen lots of benefits by cooperating, creating the market together and enjoying higher margins in 40-inch TV panels," Lee Min-hee, an analyst at CJ Investment & Securities. "They want to do it again for the bigger-size panels through the new deal."
The move comes after .
As the race of capacity expansion and competitions squeeze LCD makers' margins, analysts have forecast smaller players to join hands to survive.
S-LCD will build an "eighth generation" LCD line that uses a motherglass size of approximately 86.61 inches by 98.43 inches, the companies said.
The new line will begin mass production in the fall of 2007 and have a production capacity of 50,000 units per month.
Sony and Samsung formed the $2 billion joint venture in 2004 to make LCD panels for large TVs.
The joint venture, formed in 2004, is based in Tangjeong, South Korea, and started mass production in April, cutting panels from "seventh-generation" motherglass measuring 1.87-by-2.2 meters.
Larger motherglass enables makers to produce more panels, boosting efficiency. For example, the planned eighth-generation motherglass yields eight 46-inch TV panels, compared with six.
Samsung and Sony are aiming to sign a definitive agreement by the end of June.
Demand for large LCD panels used in personal computers is expected to rise 50 percent over the next three years, while demand for LCD panels for TVs is projected to jump more than threefold, according to research firm DisplaySearch.
Shares in Samsung Electronics ended down 1.83 percent at $672.36, underperforming the wider market's 0.29 percent decline. Sony shares fell 1.23 percent to $47.52, also lagging the Nikkei's 0.61 percent drop.
Shares in Samsung andfell on news of AU acquiring Quanta.