LG Electronics have unveiled two new giant OLED TVs with ultra-high definition screens, sticking with its strategy of using the exceptionally expensive OLED display technology.The South Korean company said it will ship 65-inch OLED TVs starting this month. A 77-inch model will hit shelves later this year.While major TV makers are pushing to make ultra HD TVs mainstream, they use LCD screens. The super-high resolution picture, also known as 4K, packs four times more pixels than regular HD televisions.Making ultra HD quality TVs with OLED screens remain costly. LG's 65-inch model will cost around BD4,400. Other types of ultra HD televisions sell for less than BD1,200.OLED features deeper colour saturation and a sharper image quality than LCD. But for years, its cost and high production error rate prevented the technology from catching on among mainstream consumers.LG said it is committed to OLED because the cost will come down and its advanced screen will eventually replace LCD screens. It forecasts that OLED TV sales will overtake LCD TV sales 'within a few years'."OLED is where we must head next," said Ha Hyun-hwoi, head of LG's TV business. "It is a matter of time."LG's aggressive bet on OLED TVs is in contrast with its rival Samsung. After rolling out a 55-inch curved TV that uses an OLED display last year, Samsung has not announced an upgrade to its OLED TV for this year. Samsung uses OLED technology mostly for small devices, such as smartphones and tablet computers.