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Comment by grishka | Hacker News Reader

Might be a dumb question, but I'll ask anyway.

In the 00s, there were reflective color LCDs in things like phones and portable game consoles. The kind that isn't black when off. Why is this technology not developed further any more, and all modern color LCDs rely on backlight? If it's a dead end, why?

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Brightness and contrast in reflective color LCDs are very poor, because the polarizing filter blocks half the light, then the color filter on each subpixel blocks a further two thirds, so a fully "white" image will only return one-sixth of the incoming light. Power efficiency has also improved for backlights, so there's less of a benefit to omitting one than there once was.

These displays can also work wonderfully, see the Amazfit Bip.

But since human vision perceives brightness logarithmically, a 6x drop still looks like a surface darker by a constant amount I think. This is an issue that regular, backlit LCDs also need to overcome.

No question reflective LCDs are rare, but you can look at the pebble smart watch or playdate game console for modern devices using reflective LCDs, for an idea of where that tech has gone.

It's just a strange set of constraints. If you need a miniscule battery, long battery life, where the device will often be used outdoors, and don't care about color accuracy at all, they're perfect.

Smartwatches are the obvious application, and it's why all Garmin watches use this tech. For most other things, it just makes more sense to sacrifice battery life or put in a bigger battery to get a massively better quality screen indoors.

Power. I don't think there were cheap blue LEDs when these displays first came out, so the backlights were all fluorescent, which was the main power draw in the display. Once LEDs came along it massively reduced the power consumption of the backlight to where it could be used even in low-power devices.

Garmin GPS watches use "transflective" displays that are always-on, daylight-readable LCDs with an optional backlight for use at night. They're not as glossy as an Apple watch, but the battery can last for a month in some modes!

The new instinct 2 solar is the first smartwatch that lasts indefinitely without plugging in. If you are outside enough it will go forever. And it has so many impressive features. We have really entered a new era, thanks largely to this screen tech.

These still exist. Some smart watches still use them.

Garmin uses them extensively in both their smart watches and handheld GPS devices like the GPSmap series. The displays are not very impressive as far as color reproduction or contrast goes, but the readability in bright sunlight is superb - way better than any LCD or OLED screen. Which is far more important for outdoor devices.

I think in the failed first e-reader wave actually used reflective LCDs. The problem was that these were quite dark and somewhat viewpoint dependent. The successful second wave (pioneered by Sony and dominated by Amazon) used electrophoresis displays by E Ink and another company I can't remember. Those were much more reflective, somewhat approaching actual paper.

The recently launched Playdate handheld gaming device uses a monochrome Sharp brand Memory LCD with no backlight.

Yeah, so the reflective LCD technology isn't quite dead. I guess when both reflectivity and quick refresh rates are required, monochrome LCD is still the only solution, since Liquavista and Mirasol were discontinued. For color displays there is simply no solution at all with decent reflectivity I believe. The E Ink Gallery 3 display seems to mostly solve the low reflectivity problem, since it does not rely on standard additive sub-pixel color mixing. But there is no similar solution for higher refresh rates. There were improved Mirasol prototypes which apparently solved the issue, but shortly after they were shown, the development of the Mirasol technology was discontinued.

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