E Ink uses microscopic ink bubbles that gets attracted to positive and negative voltages. The ink stays around when attraction stops, holding image. But the ink also require much stronger force than regular LCDs to move around.

LCDs use articulation of liquid crystal chemicals that change shape thus polarization upon application of voltages. They tend to slowly deform back to "the other" state when voltages are removed, and also tend to chemically break down if not moved back to the neutral state. LCDs are driven in pseudo-alternating current for this reason, and never held at either extremes for long time, for this reason.

So you can drive E Ink at 75Hz or whatever, it'll just take more power than it takes LCD to do so, and the last pixel states will persist. Or you can leave LCDs at extremes and disconnect the power, but it will lead to degradation if intentionally used that way.

What you can't do is 1) "watt per frame" figures of LCD, with 2) persistence, and 3) long life. (1, 3) is LCD, (2, 3) is E Ink, (1, 2) is LCD abused as if it's E Ink at expense of rapid degradation, and (1, 2, 3) is the holy grail.

▲

mcdonje 5 days ago | parent [-]

Are LCD screens driven on a pixel by pixel basis, or is the entire screen driven on each refresh? Because the article says they're only causing changed pixels to refresh.

If so, you're probably still right when it comes to watching a video or something, but e-ink could be more efficient for drawing, writing, or reading.

	▲	numpad0 5 days ago \| parent [-]
		IIUC, display controllers normally iterate rows and columns like a double for loop. The outer loop increments the row counter, inner one increments the column, and the voltage meets at the current pixel at pixels[i * j]. Most LCD controllers don't take pixel(i, j) or pixel[i * j] as the input, but expects a synchronize() signal to reset both counters followed by transfers of either row[width] in rows[height] or pixels[width * height]. The bare panel, for both LCD and EPD, would consist of a pair of glasses vapor coated with transparent indium tin oxide, chemically etched as bunch of horizontal lines on the first one and vertical in the other one, with corresponding choice of fluids suspended inbetween. It would be possible to wire a custom fabricated controller onto those row and column electrodes to drive individual pixels. I guess that is what is being done here.