LONDON — Because liquid crystal display (LCD) pixels are relatively large it is possible to integrate memory in the active memory backplane at each pixel site. Sharp Corp. has done this for a 96 x 96 pixel miniature monochrome LCD and claims a power saving of a factor of 130 compared to standard LCDs of equal size.

By including a memory at each pixel data only needs to be sent to the display as content changes from frame to frame. For most LC displays a microcontroller has to rewrite the complete screen content from frame to frame at a rate of 50- to 60-Hz even though most, or all, of the image remains the same. And it is this redundant data transmission that can waste a lot of energy.

Sharp said that its memory-LCD of 1.35 inches diagonal size consumes about 15-microwatt in operation whereas a standard LCD of comparable size needs about 2-milliwatt to render an image.

The memory-LCD has been developed based on Sharp's proprietary Continuous Grain Silicon technology. As a result, and differently from other reflective displays, the new type of LCD does not need polarisers. Thanks to a special liquid crystal material the image is generated by the status of the pixel just changing from black to white with a reflectivity of 50 percent. As a result of the low power consumption small-size solar cells can provide enough electricity to drive memory-LCDs, Sharp said.

The display is therefore suitable for portable applications such as wrist watches, heart-rate meters and other fitness devices and price tags. Samples of the memory-LCD are available starting Q2 2009.

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