The 5.5-inch display boasts 538 pixels per inch and supports 2560 by 1440 video playback, higher than the current 1080p high-definition video format.
The technology would offer "more lifelike and crisp images" than displays currently on the market, LG said.
"The new Quad HD panel will enable users to enjoy a full view of PC-version web pages at a single glance without image distortion," it said.
Analysts say the improved visuals could come at the expense of battery life.
"There's only so much detail that a human eye can pick up in a 5.5-inch screen regardless of how many pixels you manage to cram into it," Windsor Holden from tech consultants Juniper Research told the BBC.
"Beyond a certain point there is a distinct law of diminishing returns. There's also the fact that the more pixels you have, the more work your graphics processor has to do.
"That has an impact on battery life, which is already being assaulted by a host of other applications throughout the day," he said.
Another analyst said screen resolution might become less of a distinguishing factor in the future.
"LG Display will be targeting this screen at the premium market, so showing that it is pushing the technology is important to its business," analyst Daniel Gleeson said. "But I think we're hitting the point at which consumers are going to focus on other issues when they decide which device to buy because so many handsets already feature a very high resolution."