Touchscreens adopt on-cover over in-cell
R Colin Johnson
12/22/2011 4:52 PM EST
PORTLAND, Ore.—LCD vendors worldwide are being pressured by smartphone and tablet makers to quickly integrate touch into the display itself, using in- or on-cell sensors, but slow development has prompted add-on touchscreen vendors to offer interim sensor-on-cover, touch-on-lens, and similar one-glass solutions, at least for 2012.
In 2011, over 566 million projected capacitive touchscreens were shipped for smartphones alone, according to NPD DisplaySearch (Santa Clara, Calif.), and for 2012 that number is likely to mushroom as tablets, laptops, and all-in-one PC makers adopt add-on touchscreens in lieu of integrated touch with in- and on-cell LCDs.
LCD manufacturers all have intensive efforts underway to integrate the touch function into their LCDs, but according to NPD DisplaySearch, their slow development efforts will delay the introduction of integrated touch LCD until 2013.
Adding touch sensors to LCDs is problematic since the switching operations necessary to drive the liquid crystal transistors create transients that wash-out the signal coming from integrated touch sensors. LCD vendors are currently experimenting with noise-reduction and -avoidance techniques, such as multiplexing the tasks so that driving-the-LCD and sensing-touch are performed on alternative cycles.
In the meantime, for 2012 NPD DisplaySearch predicts that smartphone, tablet, laptop and all-in-one PC vendors will increasingly turn to sensor-on-cover solutions which pattern the touch sensors using a single piece of glass, instead of the two glass plates typically required today. Sensor-on-cover also has its problems, with yields reported to be as low as 70 percent, but for 2012 at least they are available, with end-user products slated to start using them with the new year.
Today touchscreens are added on to LCDs, prompting the move to single glass solutions, whereas future LCDs will have touch built-in either with in- or on-cell sensors.