Hacker News Reader

Comment by LeoPanthera | Hacker News Reader

Whatever happened to transflective LCDs? I remember some Windows CE PDA devices had them. They were more visible in bright sunlight, and used a backlight, or sidelight, for use in the dark.

I guess they went away because their color fidelity wasn't so great in the dark, but they look absolutely amazing in sunlight.

View on HN

Transflective LCDs, a.k.a. RLCDs, are currently being sold.

There are two iterations of Sun Vision Display's 32 inch monitor, and Eyemoo recently released an Android tablet with an RLCD sceen.

I have the Eyemoo Epaper S1, and an very happy with it, despite a manufacturing flaw that caused a few sparkly dust specs to be between the screen layers. I use it with the built-in frontlight at 10-20% strength which is a good compromise between brightness and comfort.

https://www.sunvisiondisplay.com/ https://eyemootech.com/

Transflective LCDs make sense when `ambient light level x LCD transmittance^2 x backlight layer reflectivity` is brighter than `brightest white LED x diffuser transmittance x LCD transmittance`. Transmittance for run of the mill LCDs is like 40% so the bar isn't that high. The left part of above formula means white level of transflective LCDs can be as low as 15-20% ambient white.

I think what happened was super-bright white LEDs replacing early LEDs and CCFL(Cold-Cathode Fluorescent Light) backlights. iPhone up to 3GS used transflectives, but LCD on 4 and later were transmissive. That was probably the point when cheap sunlight readable backlight became viable.

Still used by GPSr units, like a bunch of Garmin models. Since they need to run for a day or more, permanently using a backlight (or OLED) is not as attractive.

Or their watches, which is part of what makes them able to have an always on display and hit e.g 20+d on my Fenix 7 (or more if you turn off continuous HR).

The comparable Epix has an AMOLED display and has to turn it off to achieve the same duration (always on turns it into ~1w)

Panasonic used to use them in the Toughbook line, but their newer machines have switched to conventional LCDs with an extremely bright backlight. IMO it's an improvement - the newer LCD looks better in all but the most extreme outdoor lighting conditions.

Many Garmin smart/sport watches also use it. I have a watch with 7+ days battery time (10+ when I don't exercise / use GPS)

Thickness is another drawback I think.

Reply on news.ycombinator.com