How E Ink Developed Full-Color e-Paper

It was the end of 2008, October, right before the holiday shopping season. Talk-show host Oprah Winfrey released her highly anticipated Favorite Things list, with the Amazon Kindle topping the gadget category. This is the moment that the concept of electronic paper, or e-paper, went mainstream. But this black-and-white, reflective display that always appeared to…

It became the tip of 2008, October, perfect sooner than the vacation wanting season. Discuss-reveal host Oprah Winfrey launched her extremely anticipated Favourite Issues list, with the Amazon Kindle topping the system class.

Right here’s the moment that the thought that of electronic paper, or e-paper, went mainstream.


But this sunless-and-white, reflective reveal that continuously perceived to be on became invented properly sooner than the Amazon Kindle made it current. Its fable started a decade earlier, in 1997, at the MIT Media Lab, when it became created by two students, J.D. Albert and Barrett Comiskey, who were inspired by their professor Joseph Jacobson.

From the very origin, e-paper gave the impact magical. It became easy on the eyes, even exterior and in interesting sunlight, where other transportable shows became unreadable. It can well stride weeks between costs while mobiles equipped with other shows barely made it thru a day (about a of them restful barely make it thru a day). Yet its limitation became obvious—photos might well well appear entirely in sunless and white. In a world that hadn’t seen a monochrome reveal in a extremely lengthy time—TVs made the swap within the 1960s, pc monitors within the unimaginative ’80s—a monochrome reveal became positively quaintly outdated college.

So, for the reason that initial trend of electronic ink, because the classic abilities at the inspire of e-paper is acknowledged, and even extra with the open of the Kindle, a broad request hung over e-paper: When would we peek this magical reveal in perfect, blazing coloration?It’s no longer that folks hadn’t been attempting. Digital-ink researchers had been pursuing coloration e-paper for years, as had other researchers spherical the sphere, in universities, company be taught labs, and startups. They came up with some early merchandise that focused shelf labels for brick-and-mortar retail stores and additionally for signage. But these added perfect one coloration to a sunless-and-white screen—crimson or yellow—and that wasn’t anybody’s thought of a elephantine-coloration reveal. Indeed, bigger than a decade after that first Kindle, and larger than two a long time after its invention, elephantine-coloration e-paper had restful no longer reached the patron market.

Why did it buy goodbye for e-paper to make that Wizard-of-Ouncestransition from sunless and white to coloration? Over the years, researchers tried several approaches, some taking applied sciences from extra dilapidated shows, others evolving from the fashioned e-paper’s distinctive compile. Qualcomm, as an instance, spent billions pursuing an attain inspired by butterfly wings. Overall, the path to successful coloration e-paper is a classic, if tortuous, epic of tech triumph. Be taught on to discover why this seemingly easy declare became entirely realized perfect two years ago at E Ink, where we’re chief technical officers.

Three transparent spheres containing small circles of black and white sit under a panel split into three segments, one red, one green, and one blue. Yellow lines indicate light passing through the panel and reflecting from the spheres In E Ink’s Triton and Kaleido shows, coloration filters turn mild mirrored from white particles into crimson, inexperienced, and blue subpixels. This attain, then once more, reduces resolution and brightness, limiting the popularity of the most fundamental generation of the abilities.James Provost

Nowadays, E Ink’s elephantine-coloration ePaper is in consumer arms, in merchandise along with e-readers and smartphones and demonstrate-taking devices, and from roughly a dozen manufacturers. These consist of the Guoyue Smartbook V5 Coloration, the HiSense A5C Coloration Smartphone, the Onyx Boox Traipse 2 Coloration, and the PocketBook Coloration. Simplest one other elephantine-coloration electronic paper product has been announced—DES (Show Digital Slurry) from China’s Dalian Factual Show. At this writing, no devices the usage of DES have shipped to consumers, although a handful of journalists have obtained samples and two Kickstarter campaigns characteristic merchandise designed to expend the reveal.

The declare stemmed from the nature of the abilities. Dusky-and-white electronic ink is a easy fusion of chemistry, physics, and electronics, and it does glorious a lot what dilapidated ink and paper does. E Ink’s version is manufactured from microcapsules of negatively charged sunless particles and positively charged white particles—the identical pigments aged within the printing industry this day—floating in optimistic liquid. Every microcapsule is regarding the width of a human hair.

To have our ePaper reveal, we initiate by making batches of this electronic ink, then expend it to coat a plastic substrate some 25 to 100 micrometers thick, looking out on which product it’s supposed for. We then lower the rolls of lined movie into the desired reveal dimension and add skinny-movie transistors to label electrodes above and below the ink layer, which is sandwiched between retaining sheets, and, presumably, touch panels or entrance lights.

To manufacture a image, an ePaper tool applies different voltages to the tip and backside electrodes to label an electrical discipline. On the tip, the voltage is end to zero, and at the backside it alternates among –15, 0, or 15. Every time the image on the screen desires to trade, a particular sequence of voltages utilized to the backside electrode moves the particles from their outdated space to the gap fundamental to reveal the lawful coloration for the new image. This update time on the final takes lower than half of a 2nd.

Bringing white particles to the tip of the reveal creates the looks of “paper”; sunless ones label “ink.” But the particles don’t must sit down down at the very prime or very backside; after we cease producing that electrical discipline, the particles cease in their tracks. This vogue we can label a combination of sunless-and-white particles come the tip of the reveal—acting as shades of grey.

Five trapezoids, labeled respectively green, orange, black, white, and yellow, contain different arrangements of small magenta, white, yellow, and cyan circles. E Ink’s Evolved Coloration ePaper (ACEP) makes expend of four different forms of pigment particles, varying in dimension and price. The system applies varying electrical fields to push and pull them to different positions in each trapezoidal microcup to label the desired colours.James Provost

The utility that determines the timing and the voltages utilized to each electrode is complex. The picks rely on what became beforehand displayed at that pixel. If a sunless pixel in one image shall be sunless once more within the subsequent image, as an instance, no voltage desires to be utilized at that position. We additionally wish to be cautious with the transitions; we don’t desire a outdated image to linger, but we don’t desire an abrupt trade to delay the screen to flash. These are nevertheless about a of the factors we took into consideration when designing the algorithms, known as waveforms, that we expend to assign the sequence of voltages. Designing them is as a lot art as science.

To carry coloration into the equation vastly complicates the waveforms. Dusky and white is a truly easy dichotomy, provided that an electrical discipline can label both a definite or a negative price. That stretch can’t accommodate elephantine-coloration digital paper. We fundamental something fully new.

We started exploring choices within the early 2000s. Indubitably one of our first commercially launched coloration merchandise, in 2010, aged a coloration filter—an array of squares printed onto a layer of glass placed on prime of the fashioned sunless-and-white ink layer. When we utilized a price to switch the white particles to the skin at a chosen position, the mild would jump inspire to the viewer thru the crimson, inexperienced, or blue filter above it. It became an obvious attain: All of the colours seen to other americans might well well additionally be created with combos of crimson, inexperienced, and blue mild, which is why most of this day’s most classic reveal applied sciences, delight in LCDs and OLEDs, expend RGB emitters or coloration filters.

We known as our product E Ink Triton. Whereas an electronic textbook did open with the abilities, the most fundamental part this effort taught us became what would no longer work for the patron market. Its resolution became just too low and the colours no longer interesting enough for these that were aged to the high resolution of capsule computers or print magazines.

The brightness declare stemmed from the reality that unlike LCDs and OLEDs, which, respectively, expend a backlight or emit mild directly, E Ink’s shows are fully reflective. That’s, mild from an exterior supply goes thru the clear quilt, hits the ink layer, and bounces inspire to the viewer’s eyes. This diagram is big for exterior expend, because of reflective shows are enhanced rather then washed out by interesting sunlight. And the shows are perfect for factor in comfort, because of they don’t shine mild directly at a user. But with a reflective system, every layer between the ink and factor in absorbs or scatters about a of the mild. Adding that coloration filter layer, it grew to change into out, precipitated fundamental dimming.

Seven panels are showing in a blown-out stack, the top and bottom frame the middle five, labeled front light, touch panel, color filter, micro capsules, and TFT For its Kaleido coloration reveal, E Ink integrated a entrance mild and patterned the coloration filters as a series of short strains to pork up brightness, coloration saturation, and contrast.James Provost

As properly as, the usage of a coloration filter to split monochrome pixels into three colored pixels reduced the final resolution. A reveal originally having a resolution of 300 pixels per crawl, with an addition of a 3-coloration filter, now has a resolution of 100 pixels per crawl. This became no longer as a lot of an argument for a 32-crawl reveal aged as a signal—pixel sizes might well well presumably be larger, and big letters don’t require high resolution. On the opposite hand it became an actual declare for itsy-bitsy fonts and line drawings on handheld devices.

Whereas our researchers were rising with this filtered reveal, others in our labs thinking about a special attain, known as multipigment, that didn’t rely on coloration filters. On the opposite hand, that attain requires far extra refined chemistry and mechanics.

Multipigment e-paper additionally shares fundamentals with its monochrome predecessors. On the opposite hand, as an different of entirely two forms of particles, there are now three or four, looking out on the colours chosen for a particular application.

We fundamental to derive these particles to acknowledge uniquely to electrical fields, no longer simply be attracted or repelled. We did about a things to our ink particles to enable them to be better sorted. We made the particles different sizes—larger particles will typically switch extra slowly in liquid than smaller ones. We various the costs of the particles, taking earnings of the reality that price is extra analog than digital. That’s, it might perchance well additionally be very certain, a bit of certain, very negative, or a bit of negative. And rather a range of gradations in between.

When we had our particles differentiated, we had to adapt our waveforms; as an different of fine sending one set of particles to the tip as but any other goes to the backside, we each push and pull them to label a image. As an illustration, we can push particles of one coloration to the tip, then pull them inspire a bit of so that they combine with other particles to label a particular colour. Cyan and yellow together, as an instance, manufacture inexperienced, with white particles offering a reflective background. The nearer a particle is to the skin, the larger the intensity of that coloration within the combine.

We additionally changed the form of our container, from a sphere to a trapezoid, which gave us better protect watch over over the vertical space of the particles. We call these containers Microcups.

For the three-particle system, now on the market as E Ink Spectra and aged essentially in electronic shelf labels (ESLs), we assign sunless, white, and crimson or sunless, white, and yellow pigments into each Microcup. In 2021, we added a fourth particle to this method; our new generation makes expend of sunless, white, crimson, and yellow particles. These are big for producing deeply saturated colours with high contrast, nevertheless these four colours can no longer be mixed to label elephantine-coloration photos. This abilities became first launched in 2013 for retail ESLs. Companies have built E Ink shows into hundreds and hundreds of these tags, transport them actual thru the sphere to outlets similar to Simplest Preserve end, Macy’s, and Walmart. Identical electrophoretic shelf labels that expend shows from China’s DKE Co. have since approach on the market.

For our factual, elephantine-coloration system, which we call Evolved Coloration ePaper (ACeP), we additionally expend four particles, nevertheless we now have dropped the sunless and rely on white—our paper—along with cyan, magenta, and yellow, the colours aged in inkjet printers. By stopping the particles at different phases, we can expend these particles to label up to 50,000 colours. The following reveal renders colours delight in these in newspapers or even watercolor art.

Hands hold a tablet with a color display The PocketBook Inkpad 3 Legitimate, presented in 2021, makes expend of the 2nd-generation E Ink Kaleido Plus coloration revealPocketBook

E Ink launched ACeP as E Ink Gallery in 2016. Again, it wasn’t acceptable for consumer devices, because of of unimaginative refresh rates. Additionally, as it’s a reflective reveal and not utilizing a backlight, the colours were too muted for consumers aware of interesting smartphone and capsule shows. For now, it has been geared predominantly in opposition to expend in retail signs in Asia.

Realizing we restful weren’t hitting the patron-market sweet position with our coloration shows, our R&D crew went inspire to buy but any other spy at Triton, the system that aged RGB coloration filters. What worked and what didn’t? Were there adjustments shall we make to at last manufacture a coloration e-reader that customers would desire?

We knew the filters were sapping brightness. We were glorious certain shall we greatly slit inspire this loss by getting the filters nearer to the electronic ink.

We additionally fundamental to amplify the resolution of the shows, which intended a a lot finer coloration-filter array. To derive a resolution extra in line with what consumers are aware of, we had to shoot for at the least 200 pixels per square crawl. That’s about twice the density we were ready to form with our first spherical of Triton shows.

When in contrast with the complexity of formulating inks with a vary of costs, as we had done in rising ACeP, you would possibly well well think this might perchance had been easy. On the opposite hand it ended up requiring a new abilities to print the coloration filters on the glass substrate.

We had created our earlier filters by printing semi-clear crimson, inexperienced, and blue ink on glass. But this glass became an added layer. So we determined to print directly onto the plastic movie that holds the tip electrode, along with this step after our reveal modules were nearing the tip of the assembly route of. This diagram would derive the filters as end to the electronic ink as possible. It can well additionally enable us to amplify resolution, because of aligning the filters with the reveal pixels might well well presumably be done extra exactly than became possible when the usage of a separate surface.

We found the form of printer we can have liked at the German firm Plastic Good judgment, a companion of E Ink for the reason that early days of the firm. But this printer became supposed for expend in an R&D lab, no longer for high-volume production. The processes it aged wanted to be converted to operate in a special, production-ready machine.

We additionally fundamental to establish out new printing patterns for the coloration filter. These are the staunch shapes and arrangements of the crimson, blue, and inexperienced filters. We had found thru working on Triton that printing the filters as a straightforward square grid became no longer the finest possibility, because the pattern might well well presumably be seen during optimistic image transitions. And so the hunt for the perfect pattern became on. We went thru many iterations, serious regarding the perspective at which mild hit the reveal, as this perspective might well well without wretchedness shift the coloration seen by the user. We evaluated a grid, straight printed strains, lengthy strains, and a host of other designs, and settled on a pattern of short strains.

Because right here’s a reflective reveal, the extra mild hitting the reveal, the brighter it is. The be taught crew determined so that you can add a entrance mild to the reveal, something that became no longer allotment of Triton, working exhausting to be certain the mild rays hit the ink layer at an perspective that maximizes reflectivity. The expend of a entrance mild will enhance vitality consumption, needless to express, nevertheless it’s value it in this case.

Which ability, E Ink’s new coloration abilities, E Ink Kaleido, has greatly extra saturated colours and an even bigger contrast ratio than E Ink Triton. And at last, a elephantine-coloration electronic-ink reveal became ready for expend in consumer merchandise.

The necessary reputable batch of Kaleido shows rolled off the manufacturing line in unimaginative 2019. We started transport to customers soon after, and you would possibly well well now peek the abilities in merchandise delight in the Hisense A5C, the iFlytek Book C1, and the PocketBook Coloration, all of which had been launched in 2020. A 2nd generation of Kaleido, known as Kaleido Plus, started transport in early 2021, with merchandise launched by Onyx and PocketBook and extra launching soon. This update improved coloration saturation due to the adjustments made within the printing pattern and the mild guides for the entrance mild.

Manufacturing equipment being fed by large sheets of flexible plastic bending around rollers As allotment of E Ink’s manufacturing route of, microcapsules of ink coat plastic movie. The movie is then dried, inspected, rerolled, and despatched on for extra processing.E Ink

Now we have about a things to work on. Gentle efficiency, the allotment of incoming mild that makes its method inspire out to the user’s eyes, is good nevertheless it might perchance well presumably be better. We’re persevering with to work on our movie layers to extra lower this loss.

By persevering with to refine our printing pattern, we’re additionally working to pork up resolution by the usage of denser circuitry within the electronics that sit below the ink layer and switch voltages on and off to switch the charged particles.

We’re additionally persevering with to work on our filterless, multipigment electronic-ink abilities. We request to open a new generation for expend in signage soon, and this might consist of brighter colours and sooner web page updates. In some unspecified time in the future we might well well even be ready to switch this into consumer devices.

When E Ink’s researchers set out exploring coloration electronic ink within the early 2000s, they belief it might perchance well be a subject of some years to fruition, given our abilities with the abilities. Regardless of every thing, sunless-and-white e-paper took entirely 10 years from thought to commercialization. The motorway to elephantine coloration grew to change into out to be for far longer. But, perfect delight in Dorothy within the Wizard of Oz, we at last made it over the rainbow.

This text appears within the February 2022 print declare as “E Ink’s Technicolor 2d.”