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by: Steve Sechrist
Mobile Displays - At CES Sharp made its new IGZO technology a centerpiece of the company’s presentation on Press Day that will transform displays by moving from amorphous silicon (A-Si) material to the Indium Gallium Zinc Oxide with far superior electron mobility and much smaller TFTs (thin film transistors) that significantly boost the pixel aperture ratio.
The cascading effect of these two advantages over A-Si are stunning, and Sharp is taking full advantage, as evidenced in the CES booth. The big advantage in mobile displays comes in power savings, as the larger aperture ratio allows for far fewer LED backlights to achieve the same brightness levels. But beyond the obvious power savings from fewer backlights, the high electron mobility from Sharp IGZO also allows the display panel to modulate the on/off state (at about 100 Hz) and still maintain the image on the screen, according to Chris Frank of the Sharp Camas Labs in Washington State. This, along with the ability to do a “Variable Refresh” based on content contributes significantly to the power savings, Frank told us. ”While more efficient back light illumination is the major contributor to power savings, the variable update based on content–say e-Book content versus a fully saturated video feed, allows us to drop the refresh rate to as low as 1Hz to save power.” This can drop the power requirements of the panel (excluding backlight) up to 80% according to Frank.
At the show Sharp had an IGZO panel next to a traditional LCD model with the same content. Both were hooked up to a power meter with the dynamic display showing not just an overall lower power draw, but the power modulation from cycling the on/off state of the panel. Power actually dropped to zero during display of the dynamic content, with the image remaining on the Sharp IGZO panel.
Beyond power savings, the other ground breaking enabler for the Sharp IGZO panel and its power modulation scheme is the ability create a virtually electromagnetic noise free environment during the power down state. This allows discrete sensors like the capacitive touch screen to operate much more efficiently. Masayuki (Ian) Inoue of the Sharp Microelectronics in San Jose, CA told us the power modulation will empower a whole new “class” of sensors for displays using IGZO technology with far more discrete sensitivity than previously possible.
“The high electron mobility allows display on/off state modulation that is already empowering discrete capacitance (touch) sensitivity at previously unrealized levels,” Inoue said. This can open the door to highly discrete (Bio / cellular, UV, atmospheric, even mineral) sensor enablement that can now combine with the display. In fact the Sharp IGZO technology has the potential to ”revolutionize” the sensor/display space, empowering a virtually EM noise free environment through this simple modulation scheme.
Finally, IGZO can significantly boost pixel density, with an upper limit modeled by the Sharp group that could go beyond 1000 ppi. Now that’s way beyond human visual acuity, but it does open up the possibility of new applications and markets we haven’t even begun to consider (think unintended consequences.) All these factors combine to give the Sharp IGZO technology the potential to be a key enabler in the display space going forward. We see the Sharp IGZO as a game changing compound material with the potential to usher in not just a new class display, but perhaps whole new industries as we enter the age of “sensorization” of mobile devices. – Steve Sechrist