Some years ago there was this „paperlike kindle“ that was advertised with: „you can read it in bright daylight!“ and then we never heard about this invention again.
Edit: thanks for your input. I think I understand now.
In: Technology
e-ink screens are useful when you don’t need a wide range of colors or a fash refresh rate. however, both of those are heavily valued in the context of mobile phones, so the technology just isn’t appropriate for that usage case.
Because the screen would have to be able to output more light per square inch on average than the sun. If you’ve ever looked directly at the sun, you’ll quickly realize why that’s neither practical or desirable.
There are reflective LCD displays for monitors that are only readable in sunlight because they have a mirror instead of a backlight. This is completely unusable without any light though.
there are https://hisenseeink.com/
but the technology has a very bad refresh rate, so you cant use it for games or videos, and it cant do smooth scrolling.
its also not great for color.
There are other technologies (like those in the gameboy color) that maybe could do better, but no one actually WANTS a phone like this since you would have to use an external light to read it and overall experience isnt great.
E-ink is great if you have an external light source, but it’s not good for any color or motion, let alone video playback or games, it’s generally a bad display if you’re NOT using it as an electronic book. It’s just a bad fit for the things we expect our phones to do.
In short, if we want accurate colors, fast changes to the picture (like video or even scrolling down a page), and also want to be able to use the display in the dark, we need to produce our own light behind the screen, or with newer OLEDs, directly in the screen itself.
Unfortunately, the sun is insanely bright and we have not developed technology that would lets us produce a backlight or self-lighted display that rivals the sun… we probably never will… at least not on battery power in a tiny phone.
This is a video reviewing a product that uses sunlight instead of an internal light, so it is readable in the sun. Very cool tech, but they discuss in the video why it’s not that versatile or good for regular use: [https://www.youtube.com/watch?v=c0TcGjzKbag](https://www.youtube.com/watch?v=c0TcGjzKbag)
Because everything in engineering is a trade-off. E-ink screens can be read in daylight because they’re not backlit and rely on ambient light to reflect off of or be absorbed by the white/black parts of the screen. The problem with e-ink, if you’ve ever used a kindle, is that they’re slow to update and can’t (as far as I know) do color. Those are fine limitations for basically an electronic book where you only turn the page occasionally, but if you want to watch video or have navigation tasks be responsive you have to use a traditional LCD screen which relies on a backlight that is easily overpowered by the sun.
The Kindle screen uses a technology called “e-ink”. This works by, instead of having electronic pixels, you use tiny little liquid filled beads with dark suspended pigment particles in them. If you apply an electric charge to the pixel grid, you can make those suspended particles move away from the screen, making it look bright, or move towards the screen, making it look dark.
This technology has several advantages, as you mentioned they are readable in bright daylight, because they work basically exactly the same as ink on paper, meaning the reflected glar doesn’t wash out the light produced by the screen. Other advantages are that this display technology is entirely passive if the screen isn’t changing, so it uses no power at all unless you change something, which of course makes it great for e-readers, where the screen rarely changes.
However it comes with some very significant drawbacks. Since you have to wait for the physical pigment particles to move around, changing a pixel takes very long compared to normal screens, leading to very low maximum refresh rates (typically no more than a few Hz, for comparison most phones nowaday run at least 60 Hz screens, and 24Hz is the absolute minimum if you want to be able to watch a video without visible stuttering, more if you want to view rendered content like video games). Since you’re working with these black pigment particles it also (E: usually, but not always) limits you to a black and white (or, at best, grayscale) display, and these two major drawbacks make the tech effectively useless for smartphones or tablets.
Most flagship smart phones get bright enough to be used in direct sunlight these days. Even my 1.5 yo phone can handle it quite well.
I dunno about you, but I use my eink Kindle daily. It’s great at what it does, but it would be terrible as a phone. It’s only black and white, it’s slow to change (turning pages has lag) and there’s significant carryover from one image to the next. Using it as a phone screen would be terrible, so we don’t.
Phone screens are a compromise of many things.
You want touch technology, good colour and quality. Wear resistant and somewhat safe to drop. And apparently no problems with sunlight.
On top of that you want it cheap.
So you design something that’s a compromise of many things and, if I were a phone (screen) developer, I’d rate “readable in sunlight” pretty low on that list.
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