Which LCD technology was used in Game and Watch?

Question

TL;DR -

• Was the LCD technology in Game & Watch passive (or active)?
• If so, was the technology used Twisted Nematics (and at which point, if at all, were Super Twisted Nematics employed, and in which latter models)?

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Leading on from Thomas's excellent answer to the question, Main board of the original Game & Watch (Ball), does anyone know what sort of LCD technology was used in the Game and Watch devices?

Thomas mentions that the LCD required constant refreshing (specifically for Green House, which came out in late 1982):

There is a bit more logic to it, but that's essentially it; some of the logic is to drive the screen; I don't remember the reason but I was explained that LCD screens from that era needed the segments to be toggled on / off to prevent some damage, apparently it's the same in watches; if anyone worked with that technology, I'd be happy to understand the details.

I wondered what the answer was to the need for constant toggling, and decided to research the topic.

The Wikipedia G&W - Models section lists the release dates which range from 1980 to 1991. Bearing that in mind, I looked up which LCD technologies were available at these dates.

The Wikipedia entry for the history of the LCD during the 1970s and 80s, states that Twisted Nematic (TN) field effect LCDs were available when the G&W was first conceived. Later, in 1983, Super-Twisted Nematic (STN) structure for passive matrix addressed LCDs was invented, and so would have been available for the later models of G&W.

Assuming that the TN was used, en lieu of the earlier Dynamic Scattering Mode (DSM) LCD (which was discovered in the 60s):

In 1971 the company of Fergason ILIXCO (now LXD Incorporated) produced the first LCDs based on the TN-effect, which soon superseded the poor-quality DSM types due to improvements of lower operating voltages and lower power consumption.

Presumably the LCD used was passive and not active. From Passive and Active-matrix, it is stated that STN requires constant refreshing, similar to that alluded to by Thomas in the quote above:

STN LCDs have to be continuously refreshed by alternating pulsed voltages of one polarity during one frame and pulses of opposite polarity during the next frame.

The earlier TN also requires refreshing, or toggling, see the description of Twisted Nematics. Although in this wiki entry, there is no mention of refreshing, or field reversal, it is actually required¹:

A voltage of about 1 V is required to make the crystal align itself with the field, and no current passes through the crystal itself. Thus the electrical power required for that action is very low.

So, to summarise, are my assumptions correct, and TN was used in the earlier models of G&W? Also, was STN used in latter models? If so, at which point was STN employed and for which G&W models?

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From the article Game & Watch there are a number of references to the fact that when the G&W was designed LCD screens were crude, and with limited size/resolution yet cheap and plentiful, but the actual type of LCD used in not mentioned.

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¹ The reason why polarity reversal is required is answered by this answer to the question Do Twisted Nematic LCD need refresh (polarity reversal)?

Answer 1

This is going to be hard to answer with any substantial evidence. Ideally, we'd like a hardware geek with a sharp eye to pick out hints from tear-down or upgrade videos found in the usual places.

But, we do know that the original Game and Watch design was guided by the Lateral Thinking of Withered Technology philosophy. By design, the whole platform depended on the most mature, dependable, and economical hardware available at the time.

According to Nintendo lore, this meant eschewing newer LCD tech that was faster, clearer and used less energy in favour of whatever the big standard LCD devices of the day used.

I'm actually not sure what that specific mature LCD tech would be called then or today, but that is certainly what was used for the Game and Watch platform.

But given the design constraints and the era, it was probably some sort of TN or active matrix.

Answer 2

Your assumptions are reasonable, TN is most likely.

DSM appears never to have been mainstream. TN LCDs provided better visual quality at lower power and took over pretty much as soon as they were on the market.

STN's advantage over TN is in LCD matrices — that is, big arrays of pixels like a laptop screen where individual wires for each pixel would be impractical. STN's sharper voltage-response curve makes it less prone to smearing/ghosting effects when wired up in a row/column matrix. But the Game & Watch didn't need a matrix, it used discrete LCD segments. So there was no need for the more advanced STN technology.

Any kind of actve-matrix tech (TFT et cetera) is similarly ruled out as unnecessary and expensive. When there's no matrix at all, the advantages of active over passive matrix don't come into play.