Sharp Corp exhibited several reflective LCD panels at SID Display Week 2009, an academic conference that runs from May 31 to June 5, 2009, in Texas, the US.
They include "pixel memory" type panels, which use 1-bit memory in each pixel of a TFT substrate to prevent flickering when the frame frequency is lowered, and "LCD memory" type panels, which include memory in the LCD instead of the TFT substrate.
The power consumption of the pixel memory type panel is 10 to 25μW, about 1/60 the power consumed by Sharp's 60Hz-operating reflective LCD panels, because its frame frequency can be lowered to 1Hz without concerns for flickers. The company expects the pixel memory type panels to be used like electronic-paper (e-paper).
"Its power consumption is smaller than that of general e-paper," Sharp said. "The pixel response, in particular, is nearly three times faster than e-paper."
However, its response speed is twice as slow as the company's existing reflective LCD panels.
Sharp has already started mass-production of this type of reflective LCD panels in 1.35- and 3-inch sizes. They will be used in products such as mobile phones to be released in Japan in June 2009, the company said. Although these mass-produced panels are monochrome displays, Sharp has already prototyped a color display panel as well.
"The use of a color filter for a reflective LCD results in a slightly lower luminance or greater power consumption," the company said. "These are the challenges we are facing."
Meanwhile, a 2.7-inch LCD memory type panel was exhibited next to Sharp's existing reflective LCD panel. The power consumption of the memory type panel is 495μW when it is operating at 1Hz. This is larger than that of the pixel memory type even after taking the different screen sizes into account.
"In terms of contrast, the LCD memory panel is slightly inferior to the existing LCD panel," Sharp said.