Exploring the World of E-Ink Today’s climate of progress for the sake of progress can be a little tiring. It’s easy for one to get cynical browsing Kickstarter. Exploring the World of E-Ink What I’d give to be a fly on the wall, and observe the brainstorms that I imagine went a little something like this: Ya know, innovation in teapots has really stagnated. I really wish my teapot were able to gauge my emotional state to improve my tea-drinking experience. I haven’t seen anything new in the personal hydration market; everybody’s already got a nice canteen of some sort. I know!
Exploring the World of E-Ink
Let’s put a solar panel on a water bottle and put bluetooth in it, connect it with your phone, and have it tell you when you should drink from it, because we all know that our bodies lack the biological processes necessary to signal that we need to drink fluids. But one of those brainstorms did in fact bring a popular item to market. What did that brainstorm look like? “What if we could have books…. without the book?” And thus, the e-reader was born. Now, in this video I’m not going to be talking about e-readers themselves… OK I’ll be talking a little bit about them but the main focus and attraction of today’s technological exploration is the display technology behind the world’s most popular e-readers. That would be electronic paper, or e-paper, or e-ink, or… electronic ink. E-readers had existed in some form long before e-paper appeared, in fact Techmoan made an excellent video on the Sony Data Discman from 1990 which you should totally watch, but they weren’t exactly a great experience. LCDs had weird viewing angles and were hard to see, battery life wasn’t great, and storage, being the 1990’s, was limited and relied on some sort of physical media anyway. Might as well just have a book. But the development of e-ink fixed the battery life and display problems, and by the time it became viable, flash storage was cheap enough that books could be stored permanently on the device. And remember, these are books we’re talking about, so what’s being stored is mainly text and maybe some pictures.You could fit dozens of books in just 64 megabytes. Now, let me introduce you to the device which introduced me to the word of e-ink. This is a Sony PRS-505, the second model of Sony Reader available for sale in the US.
I first saw one of these on display at my local Borders. That’s the second failed enterprise in as many sentences. Anyway, when I saw this I thought the display was fake. One of those silly demonstration units with a cardboard cutout for a screen. But when I pressed the page turn button and this happened, I was taken aback. There’s no way that screen can be real! Well, it was, and this one is. Now if you’re familiar with e-ink, which I imagine most of you are by now, this is no big deal. But back in 2006 when the Sony Reader was first launched, this was like magic. A digital display of any sort which looked like paper was mind boggling. The viewing angles are perfect, just like paper. Bring it outside, and it’s as if you’re reading an actual paper book. Even in direct sunlight, the display is perfectly easy to read. Just like paper. Now the contrast wasn’t remarkably good, about as good as a newspaper, but if you’re reading text that’s perfectly fine. And the fact the the screens were greyscale didn’t really matter, because you’re reading text. Mostly. Certainly the display technology wasn’t perfect, but because it looked and behaved as if it were a sheet of paper, it was readable in any conditions a book is, and it didn’t come with the eyestrain problems of a backlit display. So what makes it so different? Well, practically everything about it.The liquid crystal display was very mature by the time e-ink rolled around, but it relied on properties of light to make it function that lead to all sorts of problems.Every LCD needs to polarize light in order to work.
The basic theory behind LCD technology is that two perpendicularly opposed polarizing filters will block light from passing through them. Between the filters is a liquid crystal that essentially twists light and allows the incorrectly polarized light to pass through by re-aligning it with the front polarizing filter. But, when the crystal experiences a voltage passing through it, it aligns in such a waythat the light will no longer be twisted, and thus will be blocked from passing through. It’s some pretty neat stuff, I’ll admit, but the polarization as light passes through it results in viewing angle limitations. Non-backlit displays like the one in this watch have excellent contrast and viewability, but only under certain conditions. Depending on the angle of the light hitting it, it might suddenly become very dark and muddy. You really want the light source to be above you or behind you, because it needs to pass through the display and be reflected straight back for best results. If you’re not looking at the display pretty much head-on, the polarization effect is weakened, and the contrast is drastically reduced. This is what makes devices like the Game Boy Color so annoying to use. You need to find some way to get comfortable, but also have the light be behind you, or else you’ll be holding it at a weird angle the whole time you use it. Which of course was what usually happened. Giving the display a backlight fixes most of these problems–though let’s not forget the dark days of pre-IPS panel crappy viewing angles– but introduces new problems.
Most displays these days, regardless of technology, are made to appear black when they’re not on. This allows for contrast to exist between light and dark areas even in moderate ambient lighting. But when you take this display outside, now there’s so much ambient light that the display is hard to read. You can combat this with an even brighter backlight, but now you’re using a lot of energy, which isn’t great for portable devices. And no matter what you do, a glowing display in your face is likely to result in some eyestrain.In a nutshell, LCDs manipulate how light passes through them, and light has to pass through the polarizing filters in order to be manipulated. But what if we could produce a display that doesn’t require light to go through it at all.
Let’s think for a moment what makes up a printed piece of paper. The paper is white, and when light lands on it it isn’t reflected back in just one direction like a mirror, or narrowly like in an LCD. Diffuse reflection causes it to be reflected in pretty much every direction. That’s how we see normal objects. It doesn’t really matter what angle we’re looking at it from, or what angle the illumination source is coming from, because the light that hits it is scattered in all directions. To put text on paper, a pigment is added which will absorb light and prevent it from being reflected as intensely, or change the proportions of the wavelengths that get reflected, imparting what we see as color. So how could you go about making a display that emulates the appearance of paper? It needs to be diffusely reflective, in order to look like paper, and it also needs to be able to darken parts in order to form images. Well, e-ink displays are made up of tiny microcapsules that are filled with a mixture of black oil and white pigment. And in a way, each of these particles functions like a teeny tiny Etch A Sketch. See, the insides of an Etch A Sketch are black, and it’s filled with aluminum powder. When it’s shaken, the powder is thrown around with the help of polystyrene beads and coats the glass, making a uniformly silver screen.
The dials control the two axes of a plotter, and as it moves, it scrapes the aluminum off of the glass, exposing the dark insides of the toy. If you’re really patient you can scrape off enough of the screen to see the actual mechanism inside.The tiny particles in an e-ink display are quite similar in concept. Inside them is a black oily substance, with a bit of negatively charged titanium dioxide powder suspended in it. If a positive charge is produced, this will attract the white titanium dioxide toward it and cause it to bunch up against the inside surface of the microcapsule. The result is that it appears in front of the black oil, and the microcapsule appears white.
If you reverse the charge, now the titanium dioxide particles will be pushed away and end up on the opposite side of the microcapsule, revealing the black oil and thus the microcapsule appears black. Later screens use positively charged black particles as well, which although I can’t find the specific reason for doing so, likely increases contrast. By sandwiching a bunch of these microcapsules between two electrodes, you can choose to make them appear either black or white depending on the polarity of the charge you produce. So, taking it a step further, if you take a great big bunch of these microcapsules, and sandwich them between an active matrix of electrodes, you can produce a screen with given size and resolution. So long as the electrodes on the display side are transparent, you’ll be able to see the microcapsules underneath. And that’s exactly how most e-ink displays work.
The technology itself is referred to as an electrophoretic display. The concept of electrophoresis was well known before e-ink became viable, but the invention of the microencapsulated electrophoretic display led to devices like this being viable. That really has a nice ring to it, doesn’t it? Microencapsulated electrophoretic display. Rolls right off the tongue. Perhaps the signature advantage of this display technology, aside from its paper-like appearance, is that the display does not require power to produce a static image. The microcapsules are so small, and the fluid they’re suspended in is viscous enough, that the pigment particles will just stay where they are indefinitely. This is why the battery life of an e-reader is so great. Unless it’s actively changing what’s on the screen, it can essentially just turn itself off. Assuming the software was written this way, the hardware can be barely awake, just enough to register button presses.
Then it can wake up, refresh the screen, and go back to sleep until the next page turn is requested. Sony used to quote battery life of these by the number of page turns possible. In the case of this unit, that was 6,800 turns. So in theory, you could read a dozen or so books on one charge, depending on the size of the text you selected. And if I may, I’d like to digress slightly and admire the design of this unit. While buttons on things seem to have gone the way of the dodo, I really liked the aesthetic of this device, and the navigational hierarchy was clever. And here’s a neat thing–it’s got expandable storage, and –get this– a headphone jack!
That’s right, it’s an e-reader that has a headphone jack, so you can listen to MP3s while you read. What a strange world we were in back in 2007. Putting headphone jacks in things. I had a blue one, which I preferred to the silver, and while I am admittedly biased here, I think the design has aged pretty well. And, in case you’ve forgotten, this is what the first Amazon Kindle looked like. Ugh, that sure was something, wasn’t it? One of the side-effects of the microcapsules that make up the display is a sort of natural smoothing. While this display is definitely made up of pixels, in fact it has a rather measly resolution of only 800X600, each pixel contains many microcapsules, and thus the edges of the pixels are incidentally smoothed. You can definitely see them, I’m not claiming they’re not visible, but this helps to make the text seem even more natural. Thanks to a rather well-thought-out text rendering scheme, and the ability to show 8 shades of grey (actually, what’s to stop the display from showing 50 shades of grey, amirite?) [Maniacal Laughter] the edges of the text rarely seems jagged, which helps maintain the illusion that this is printed text on paper. Anywho while the screen requires no power to show a static image, you have probably noticed the weird flashing thing it does every time you change the page. And you might have also noticed how slow it is to draw any given image. Well, now we get to the downsides of epaper. Because it relies on particles physically moving within a viscous fluid, it’s not fast.
At all. This doesn’t really matter for anything an e-reader might do, but for an application like a general purpose display, it’s simply too slow to be useful. Applied Science did some experimentation on these displays, and I highly encourage checking the video out, but with current electrophoretic display technology, it’s unlikely that we could break into anything near smooth motion. The reason why this device keeps inverting the display is to avoid permanently charging any part of the screen, and thus winding up with a permanent ghost image. It also needs to do this to prevent ghosting in general. Because the particles aren’t all going to move uniformly, you can still see a very slight remnant of whatever it showed before, and without doing that inverted flash, it would be even more noticeable. Newer e-readers don’t do this with every page turn, however even in 2007 Sony wasn’t doing whole-screen refreshes for everything. The little loading animation only moves the arrows within the circle, so it’s clear that even this early on it was possible to refresh only portions of the screen. This macro-shot reveals that the the process of producing intermediate shades of grey appears to be based mainly on time. If we slow down and look frame by frame, you can see many of the pixels briefly turn a darker shade, then lighten slightly. It could be that this single frame of brief darkness is the impulse of the matrix’s charge, and the reversion to a lighter color is simply the microcapsules returning to a more relaxed state. Or perhaps the screen is briefly pulling those pixels towards black, and then a bit back to white. In fact, you can see that any pixels that are due to change spend at least some time as completely black, and completely white. They are then pulled backed to their appropriate darkness levels.
In any case, we can see clearly here that the pixels are not all manipulated at the same time nor for the same duration. And here’s where I get frustrated. E-ink development has kinda just sorta stopped. It’s not like it’s gone away, but there have basically only been incremental improvements. Sony’s later Reader models, like this PRS-350, improved on the contrast slightly, and they enabled touch support using a rather clever system of infrared emitters and receivers embedded in the bezels of the device. They also tweaked the display algorithm to quickly invert the sections you touch to affirm your input. Amazon’s PaperWhite kindles incorporate a backlight (or some built-in lighting anyway, I’m not sure of the specifics). And screens that can show either red or black have become rather common.
In fact you sometimes see these in stores in lieu of price tags. Supposedly E-Ink Holdings has developed a full-color display, but I’m not aware of any applications of it. And that’s a real shame. While I’m sure the inherent speed problems of electrophoretic technology will probably prevent it from ever breaking out of e-readers, I would love to have a computer monitor with the physical appearance of paper. I wouldn’t even mind if it were greyscale. I spend a lot of time in front of very bright, colorful computer screens, and I definitely get eyestrain from them. And although I use f.lux, a program that blocks blue light late in the evening, I still feel that the brightness alone helps keep me awake. I really only need that color and brightness for a small portion of my work. If I could use an e-ink monitor for browsing the web, writing, researching, and doing other computery things, my eyes would really appreciate it. And wouldn’t ya know it, there’s another display technology that might spread out using the principle of electrowetting. Supposedly these refresh fast enough to be suitable for video, while also having a similar appearance to e-paper. I say, let’s get on this display companies! You will gladly have my money if you come up with a paper-like display, it doesn’t even need to be full-color but if you like I’ll pay extra for it, that I can connect to my PC and use as a monitor. I would love, love, love it if I could be starting at a matte, paper-like screen, and not an eye-abusing glowing rectangle. From what it looks like, an electrowetting display could in theory also be backlit, so perhaps you could make what looks like paper when you want it to, but looks like a video screen when you don’t. Or even just, like, here. Laptop people.
I see you doing you funky stuff that no one asks for. How about a laptop with an LCD panel that happens to also have an e-paper panel on the other side, and you can just flip it around and switch to e-ink. I would bet you could boast some colossal battery life figures if you can figure out how to pull this off without a backlight. Here’s just a free idea coming at you. Figure it out, please. Regardless of my desire for a general purpose e-ink display, I’ll still happily gaze at my e-readers, marvel at the beauty of their design, and grumble about their limited applications. By the way, did you notice the connection here? Sony comes to market with a product a year before a competitor releases a very similar product, and despite Sony’s best efforts, their product failed? Where have I heard that one before? As always, thanks for watching, and I hope you enjoyed the video! I’m hoping we see more applications for e-ink, even if it’s not my pipe dream of a truly functional computer monitor. Displays have been glowing in our faces for decades and perhaps a change in that regard is worth a look. Of course, thank you to everyone who supports this channel on Patreon, especially the fine folks you see scrolling up your screen.
Your support has enabled some truly amazing things, and you all deserve my thanks. If you’d like to support the channel with a pledge of your own and get perks like early video access, behind-the-scenes videos, and the insides scoop on the latest projects, please check out my Patreon page. Thanks for your consideration, and I’ll see you next time! ♫ unfathomably smooth jazz ♫ …but, when I pressed the page turn button and this happened, I was taken aback. There’s (watch beeps) no way… I forgot I’m wearing the watch that beeps on the hour. Those microcaped… (various unintelligible mouth noises of frustration and anger) ♪ Let’s take a look at the camera ♪ Now the contrast wasn’t — oh yeah I was gonna… (clears throat) Inside them is a black oily substance with a bit of negatively charged titanium dioxide suspended in it. Titanium dioxide powder suspended in it. The result is that it appears to be in front — It is! It doesn’t appear to be. You stop messing with what you wrote, you silly person! Then it can wake up…. I didn’t plan for this