It seems that all color screens must be backlit for you to see the image. Color screens on watches, phones, digital frames, monitors, TV’s, etc. all have a light behind the screen that either produces colored light directly or illuminates colored pixels.
But black and white LCD screens are typically not backlit. Displays like LCD watches and e-readers do not have a light behind the pixels. They depend on an external light source to illuminate the screen, which may be from a builtin light on the front or just the normal light shining on the screen.
Is there any tech currently which would enable a color screen to work without being backlit? To work in a similar fashion to the B/W LCD screens where the visible light in the room provides the illumination? Some likely uses I could see would be for low-power situations (like watches) or passive displays (like digital frames).
Here’s a press release from the company that makes the electronic ink displays in some Kindle and Nook book readers, about a new color display being developed. The refresh rate is slow, though, so it’s aimed at signage for now.
The transflective LCD has been around for a while. Palm used it in some of their high-end PDAs.
It’s not widely used because it has mediocre contrast and poor color saturation. It works well in bright daylight, but everywhere else, conventional backlit LCDs look much better. Still, it’s useful when you want a low power display that’s always on. So it is used in a few smartwatches, mainly the ones that target outdoor/sport users. My Garmin Fenix-3 uses a variant of it, as do the Pebble Time and the Moto 360 Sport. I believe Garmin’s VIRB action camera uses it too.
Strictly speaking, OLEDs aren’t backlit.
What you want is a reflective color display. As mentioned above, there are color e-ink displays, but they are very slow. Work is being done on electronic chromatophore display technology, but it’s far from commercialization.
I’m pretty sure the Pebble Time display is a transflective LCD, not E Ink. Pebble refers to it as “e-paper” but that’s just a generic term for daylight-visible displays, and does not refer to a specific technology.
I feel like everyone is avoiding mentioning the Game Boy Advance because the display was so poor by modern standards. But, isn’t it exactly what the OP describes: a non-backlit color screen?
<old_man> Back in my day we carried around a separate light just to see our screens, and we liked it that way! None of this fancy back-light nonsense! </old_man>
The technology has existed for a while; the Game Boy Color had a reflective (i.e. non-backlit) color LCD in 1998.
I suspect that the reason backlit displays have become standard since then is the rapidly falling cost of white LEDs, combined with advances in battery technology. White LEDs didn’t really exist before the mid-90s, and they weren’t really cheap until at least the early 2000s. Before then, if you wanted a small white light source you were pretty much stuck with a miniature incandescent bulb, which would consume energy at a pretty good clip. But since LEDs are substantially more efficient that incandescent bulbs, their advent made it much easier to build in a light source that wouldn’t drain the battery; and having the light source allows for usability in a broader range of situations.
ETA: Emerald Hawk makes much the same point I did, though I seem to have “out-oldmanned” him by about three years.
And it’s possible to make e-ink in any single color you choose, not just black. That still doesn’t get you multiple colors, but it might be enough for some applications.
I don’t think I’ve seen any color e-ink screen in person. What would you compare the quality to? How close are they to a printed photo? I’d love to have a digital frame that wasn’t backlit so it was more like a normal photo in a frame.
I haven’t seen one live, either, but have long been a fan of electrophoretic displays, so I have read many reviews of the color screens. Unfortunately, they don’t look very good compared to other technologies. Check out this comparison (from 2012, but I don’t think things have improved much since then.)
E Ink had a demo of its Advanced Color ePaper (ACeP) at SID 2016 in San Franciso earlier this year.
There’s an article about it here with a video. One very noticeable point is that the refresh process is rather slow, requiring multiple passes to ‘set’ the image in full colour.
Color displays are going to absorb a lot of light so you’ll need more illumination than a B&W device if it’s not backlit. The light source is going to affect the colors you see also, although mostly you’ll have a pretty good white light source anyway.
The update process really does look horrible. I mean, I applaud the effort and achievement in producing this technology, but it’s a bad fit for most consumer devices such as ebooks - having to sit through 5 to 10 seconds of seizure-inducing at each page turn simply isn’t going to work.
I’m not sure that this can be improved either - as far as I understand it, the colour effect is achieved by having an assortment of different pigment particles in each pixel, each colour being a slightly different size - and the flashing effect is the system electrostatically shaking the right ones to the top.
