Sharp Begins to Roll Out IGZO TFT-based LCD Panel
Sharp Corp announced April 13, 2012, that it has started volume production of a high-resolution LCD panel using IGZO (In-Ga-Zn-O) TFTs, which are oxide semiconductors, as driver elements at Kameyama Plant No. 2.
Sharp started the volume production in March 2012 and plans to start full-scale volume production in April 2012. So, what the company claims is the world's first volume production of IGZO TFT-based high-resolution LCD panel will begin three months behind schedule (within 2011).
The high-resolution LCD panel is targeted at tablet computers. When asked about the purchaser and specifications of the panel, Sharp said, "We do not comment on customer information." And the company did not answer any questions about Apple Inc's iPad, for which the LCD panel is rumored to be supplied.
Sharp is currently planning to provide IGZO TFT-based LCD panels not only for tablet computers but for "Ultrabook" computers, high-resolution medical monitors, etc.
This time, Sharp showed 32-inch 3,840 x 2,160-pixel (4k, resolution: 140ppi), 10-inch 2,560 x 1,600-pixel (resolution: 300ppi) and 7-inch 1,280 x 800-pixel (resolution: 217ppi) panels in addition to the 11-inch 1,366 x 800-pixel panel that was announced in April 2011. The 32-, 10- and 7-inch panels are targeted at high-resolution monitors, Ultrabook computers and tablet computers, respectively.
Sharp has already started to ship samples of the three panels, and they can be mass-produced upon request, the company said.
3 features emphasized
The IGZO TFT was developed by Sharp in cooperation with Semiconductor Energy Laboratory Co Ltd. Its carrier mobility and on-state current are about 20-50 and 20 times, respectively, higher than those of amorphous silicon (Si) TFTs, which are used for large-size LCD panels, the company said. Also, its off-leak current is 1pA or lower, it said.
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With those characteristics, IGZO TFT-based LCD panels can realize (1) higher resolution, (2) lower power consumption and (3) higher performance of touch panel, compared with amorphous TFT-based LCD panels, Sharp said.
As for the higher resolution, because of the high carrier mobility of the panel, it is possible to reduce TFT size by about 75%, compared with the size of an amorphous Si TFT, the company said. In addition, by using a technique to reduce the thickness of gate/source lines, it becomes possible to double resolution without lowering transmittance, the company said.
Lower power consumption
In regard to the lower power consumption, the smaller TFT size enables to increase the use efficiency of backlight. Moreover, because of the low off-leak current, it became possible to maintain the orientation control of liquid crystal molecules even when drive frequency is reduced from 30-50Hz, which is common, to 2-5Hz.
When displayed data is not being changed much (e.g. when a standby screen or a photo is displayed), it is possible to stop driving TFTs for some time, and, therefore, the power consumption of the panel (excluding its backlight) can be reduced by 80-90%, Sharp said.
Higher performance of touch panel
Lastly, as for the higher touch panel performance, touches are detected when TFTs are not being driven. Because the influence of the noise generated by driving TFTs is eliminated, the detection sensitivity of the capacitive touch panel can be improved.