Memory LCD Technology

New displays enable more content, low power
consumption, and simple connectivity

Memory LCD Technology

Display technology advances such as LED backlighting have dramatically changed the game of LCD power consumption. However, the power requirements of some conventional LCDs can still be high enough to limit their usage pattern or usage environment.

The industry's first incarnation of memory LCD technology yielded cholesteric, electrophoretic, and other bi-stable technologies. However, these types of displays require relatively high driving voltages and considerable time to respond, in some cases requiring most of a second to update display images. They are also extremely limited in the amount of content they can display at one time.

Electrophoretic displays have also been known to experience image retention. Some current display technologies eliminate this possibility by designing a display to update twice. The first update is with a negative image to completely switch states in the display, and the second update is with the new positive image. Thus, the true update (or "refresh") rate in a typical application of this type may actually be twice that which is stated in its specifications. Due to this, even though electrophoretic displays do deliver energy savings when holding state, power drain during image updates is a real concern.

Meet Sharp's Memory LCD

Now, Sharp breaks down the barriers. Sharp's Memory LCD technology delivers a high-contrast, high-resolution display that allows for denser content than many other types of same-sized LCDs. It also eliminates sweeping images or "ghosting," because only the part of the image that requires updating needs to be changed.

With the new Sharp Memory LCD, embedded 1-bit memory in every pixel enables each pixel to hold state while requiring very little current. This delivers an "always on" display that uses little power (only a single supply voltage is required), even when updating images. This helps designers create products with exceptionally long battery life.

The response time of the Memory LCD makes it fast enough to display motion video. Bold and crisp black images are delivered by high-resolution capability in a small diagonal display.

A lightweight, two-glass design plus an integrated driver in the panel provides an exceptionally thin module that's a perfect solution for compact handheld, wrist-top, and other small-screen devices that benefit from displaying rich content. Incorporating the Memory LCD into a design is simple with 3-wire SPI serial interface (SI, SCS, SCK).

PNLC and HR-TFT Modules

Sharp's Polymer Networked Liquid Crystal (PNLC)-type Memory LCD is composed of a PNLC layer formed between a transparent surface electrode and mirror-reflective pixel electrodes. The PNLC module uses a scattering mode and does not require polarizers, which results in a very bright reflective display. A 1-bit memory circuit is embedded into each pixel, which retains the pixel information once it's written.

Sharp's high-contrast HR-TFT technology adds a polarizer to the top layer to greatly enhance the contrast of the display. The black level is dramatically enhanced, resulting in an almost paper-like black and white image.