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HomeTecnologíaHow E Ink Developed Full-Colour e-Paper

How E Ink Developed Full-Colour e-Paper


It was the top of 2008, October, proper earlier than the vacation purchasing season. Discuss-show host Oprah Winfrey launched her extremely anticipated Favourite Issues listing, with the Amazon Kindle topping the gadget class.

That is the second that the idea of digital paper, or e-paper, went mainstream.

However this black-and-white, reflective show that at all times seemed to be on was invented nicely earlier than the Amazon Kindle made it well-known. Its story started a decade earlier, in 1997, on the
MIT Media Lab, when it was created by two college students, J.D. Albert and Barrett Comiskey, who had been impressed by their professor Joseph Jacobson.

From the very starting, e-paper appeared magical. It was simple on the eyes, even open air and in brilliant daylight, the place different transportable shows grew to become unreadable. It may go weeks between expenses whereas mobiles outfitted with different shows barely made it via a day (a few of them nonetheless barely make it via a day). But its limitation was apparent—photographs may seem solely in black and white. In a world that hadn’t seen a monochrome show in a really very long time—TVs made the change within the Sixties, pc displays within the late ’80s—a monochrome show was undoubtedly quaintly old-fashioned.

So, for the reason that preliminary growth of digital ink, as the fundamental know-how behind e-paper is thought, and much more with the discharge of the Kindle, an enormous query hung over e-paper: When would we see this magical show in good, blazing shade?It’s not that folks hadn’t been making an attempt. Digital-ink researchers had been pursuing shade e-paper for years, as had different researchers all over the world, in universities, company analysis labs, and startups. They got here up with some early merchandise that focused shelf labels for brick-and-mortar retail shops and likewise for signage. However these added only one shade to a black-and-white display—crimson or yellow—and that wasn’t anyone’s concept of a full-color show. Certainly, greater than a decade after that first Kindle, and greater than twenty years after its invention, full-color e-paper had nonetheless not reached the patron market.

Why did it take so lengthy for e-paper to make that Wizard-of-Oz transition from black and white to paint? Through the years, researchers tried a number of approaches, some taking applied sciences from extra conventional shows, others evolving from the unique e-paper’s distinctive design. Qualcomm, for instance, spent billions pursuing an strategy impressed by butterfly wings. General, the trail to profitable shade e-paper is a traditional, if tortuous, story of tech triumph. Learn on to seek out out why this seemingly simple problem was solely realized simply two years in the past at E Ink, the place 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, shade filters flip gentle mirrored from white particles into crimson, inexperienced, and blue subpixels. This strategy, nevertheless, reduces decision and brightness, limiting the recognition of the primary technology of the know-how.James Provost

Right now, E Ink’s full-color ePaper is in shopper arms, in merchandise together with e-readers and smartphones and note-taking units, and from roughly a dozen producers. These embrace the Guoyue Smartbook V5 Colour, the HiSense A5C Colour Smartphone, the Onyx Boox Poke 2 Colour, and the PocketBook Colour. Just one different full-color digital paper product has been introduced—DES (Show Digital Slurry) from China’s Dalian Good Show. At this writing, no units utilizing DES have shipped to customers, although a handful of journalists have obtained samples and two Kickstarter campaigns function merchandise designed to make use of the show.

The problem stemmed from the character of the know-how. Black-and-white digital ink is an easy fusion of chemistry, physics, and electronics, and it does just about what conventional ink and paper does. E Ink’s model is product of microcapsules of negatively charged black particles and positively charged white particles—the identical pigments used within the printing business right this moment—floating in clear liquid. Every microcapsule is in regards to the width of a human hair.

To fabricate our ePaper show, we begin by making batches of this digital ink, then use it to coat a plastic substrate some 25 to 100 micrometers thick, relying on which product it’s supposed for. We then minimize the rolls of coated movie into the specified show measurement and add thin-film transistors to create electrodes above and under the ink layer, which is sandwiched between protecting sheets, and, presumably, contact panels or entrance lights.

To supply a picture, an ePaper machine applies totally different voltages to the highest and backside electrodes to create an electrical subject. On the high, the voltage is near zero, and on the backside it alternates amongst –15, 0, or 15. Each time the picture on the display wants to alter, a selected sequence of voltages utilized to the underside electrode strikes the particles from their earlier place to the place wanted to point out the right shade for the brand new picture. This replace time sometimes takes lower than half a second.

Bringing white particles to the highest of the show creates the looks of “paper”; black ones create “ink.” However the particles don’t have to take a seat on the very high or very backside; after we cease producing that electrical subject, the particles cease of their tracks. This implies we will create a combination of black-and-white particles close to the highest of the show—showing as shades of gray.

Five trapezoids, labeled respectively green, orange, black, white, and yellow, contain different arrangements of small magenta, white, yellow, and cyan circles.
E Ink’s Superior Colour ePaper (ACEP) makes use of 4 several types of pigment particles, various in measurement and cost. The system applies various electrical fields to push and pull them to totally different positions in every trapezoidal microcup to create the specified colours.James Provost

The software program that determines the timing and the voltages utilized to every electrode is advanced. The alternatives rely upon what was beforehand displayed at that pixel. If a black pixel in a single picture might be black once more within the subsequent picture, for instance, no voltage must be utilized at that spot. We additionally should watch out with the transitions; we don’t need a earlier picture to linger, but we don’t need an abrupt change to trigger the display to flash. These are however a couple of of the components we took into consideration when designing the algorithms, known as waveforms, that we use to set the sequence of voltages. Designing them is as a lot artwork as science.

To deliver shade into the equation tremendously complicates the waveforms. Black and white is an easy dichotomy, on condition that an electrical subject can create both a optimistic or a detrimental cost. That strategy can’t accommodate full-color digital paper. We wanted one thing fully new.

We began exploring choices within the early 2000s. Considered one of our first commercially launched shade merchandise, in 2010, used a shade filter—an array of squares printed onto a layer of glass positioned on high of the usual black-and-white ink layer. Once we utilized a cost to maneuver the white particles to the floor at a specific spot, the sunshine would bounce again to the viewer via the crimson, inexperienced, or blue filter above it. It was an apparent strategy: All the colours seen to people will be created with combos of crimson, inexperienced, and blue gentle, which is why most of right this moment’s most typical show applied sciences, like LCDs and OLEDs, use RGB emitters or shade filters.

We known as our product E Ink Triton. Whereas an digital textbook did launch with the know-how, the primary factor this effort taught us was what would not work for the patron market. Its decision was just too low and the colours not brilliant sufficient for individuals who had been used to the excessive decision of pill computer systems or print magazines.

The brightness drawback stemmed from the truth that in contrast to LCDs and OLEDs, which, respectively, use a backlight or emit gentle instantly, E Ink’s shows are absolutely reflective. That’s, gentle from an out of doors supply goes via the clear cowl, hits the ink layer, and bounces again to the viewer’s eyes. This association is nice for out of doors use, as a result of reflective shows are enhanced relatively than washed out by brilliant daylight. And the shows are good for eye consolation, as a result of they don’t shine gentle instantly at a person. However with a reflective system, each layer between the ink and eye absorbs or scatters a few of the gentle. Including that shade filter layer, it turned out, brought about vital 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 shade show, E Ink included a entrance gentle and patterned the colour filters as a collection of quick strains to enhance brightness, shade saturation, and distinction.James Provost

As well as, utilizing a shade filter to separate monochrome pixels into three coloured pixels decreased the general decision. A show initially having a decision of 300 pixels per inch, with an addition of a three-color filter, now has a decision of 100 pixels per inch. This was not as a lot of a difficulty for a 32-inch show used as an indication—pixel sizes could possibly be bigger, and large letters don’t require excessive decision. However it was an actual drawback for small fonts and line drawings on handheld units.

Whereas our researchers had been developing with this filtered show, others in our labs targeted on a special strategy, known as multipigment, that didn’t depend on shade filters. Nonetheless, that strategy requires much more difficult chemistry and mechanics.

Multipigment e-paper additionally shares fundamentals with its monochrome predecessors. Nonetheless, as an alternative of solely two forms of particles, there at the moment are three or 4, relying on the colours chosen for a selected utility.

We wanted to get these particles to reply uniquely to electrical fields, not merely be attracted or repelled. We did a couple of issues to our ink particles to permit them to be higher sorted. We made the particles totally different sizes—bigger particles will typically transfer extra slowly in liquid than smaller ones. We assorted the costs of the particles, profiting from the truth that cost is extra analog than digital. That’s, it may be very optimistic, just a little optimistic, very detrimental, or just a little detrimental. And numerous gradations in between.

As soon as we had our particles differentiated, we needed to adapt our waveforms; as an alternative of simply sending one set of particles to the highest as one other goes to the underside, we each push and pull them to create a picture. For instance, we will push particles of 1 shade to the highest, then pull them again just a little so that they combine with different particles to create a selected shade. Cyan and yellow collectively, for instance, produce inexperienced, with white particles offering a reflective background. The nearer a particle is to the floor, the higher the depth of that shade within the combine.

We additionally modified the form of our container, from a sphere to a trapezoid, which gave us higher management over the vertical place of the particles. We name these containers Microcups.

For the three-particle system, now available on the market as E Ink Spectra and used primarily in digital shelf labels (ESLs), we put black, white, and crimson or black, white, and yellow pigments into every Microcup. In 2021, we added a fourth particle to this technique; our new technology makes use of black, white, crimson, and yellow particles. These are nice for producing deeply saturated colours with excessive distinction, however these 4 colours can’t be mixed to create full-color photographs. This know-how was first launched in 2013 for retail ESLs. Firms have constructed E Ink screens into tens of millions of those tags, transport them all through the world to retailers corresponding to Finest Purchase, Macy’s, and Walmart. Comparable electrophoretic shelf labels that use shows from China’s DKE Co. have since come available on the market.

For our true, full-color system, which we name Superior Colour ePaper (ACeP), we additionally use 4 particles, however we have now dropped the black and depend on white—our paper—together with cyan, magenta, and yellow, the colours utilized in inkjet printers. By stopping the particles at totally different ranges, we will use these particles to create as much as 50,000 colours. The ensuing show renders colours like these in newspapers and even watercolor artwork.

Hands hold a tablet with a color display
The PocketBook Inkpad 3 Professional, launched in 2021, makes use of the second-generation E Ink Kaleido Plus shade showPocketBook

E Ink launched ACeP as E Ink Gallery in 2016. Once more, it wasn’t applicable for shopper units, due to gradual refresh charges. Additionally, because it’s a reflective show with out a backlight, the colours had been too muted for customers accustomed to brilliant smartphone and pill shows. For now, it has been geared predominantly towards use in retail indicators in Asia.

Realizing we nonetheless weren’t hitting the consumer-market candy spot with our shade shows, our R&D crew went again to take one other have a look at Triton, the system that used RGB shade filters. What labored and what didn’t? Had been there modifications we may make to lastly produce a shade e-reader that buyers would need?

We knew the filters had been sapping brightness. We had been fairly positive we may considerably scale back this loss by getting the filters nearer to the digital ink.

We additionally wished to extend the decision of the shows, which meant a a lot finer color-filter array. To get a decision extra in step with what customers are accustomed to, we needed to shoot for no less than 200 pixels per sq. inch. That’s about twice the density we had been capable of obtain with our first spherical of Triton shows.

In contrast with the complexity of formulating inks with quite a lot of expenses, as we had accomplished in growing ACeP, you would possibly assume this could have been simple. However it ended up requiring a brand new know-how to print the colour filters on the glass substrate.

We had created our earlier filters by printing semi-transparent crimson, inexperienced, and blue ink on glass. However this glass was an added layer. So we determined to print instantly onto the plastic movie that holds the highest electrode, including this step after our show modules had been nearing the top of the meeting course of. This association would get the filters as near the digital ink as doable. It could additionally permit us to extend decision, as a result of aligning the filters with the show pixels could possibly be accomplished extra exactly than was doable when utilizing a separate floor.

We discovered the kind of printer we wanted on the German firm Plastic Logic, a associate of E Ink for the reason that early days of the corporate. However this printer was supposed to be used in an R&D lab, not for high-volume manufacturing. The processes it used needed to be transformed to function in a special, production-ready machine.

We additionally wanted to determine new printing patterns for the colour filter. These are the precise shapes and preparations of the crimson, blue, and inexperienced filters. We had discovered via engaged on Triton that printing the filters as a easy sq. grid was not the most suitable choice, because the sample could possibly be seen throughout sure picture transitions. And so the hunt for the right sample was on. We went via many iterations, contemplating the angle at which gentle hit the show, as this angle may simply shift the colour seen by the person. We evaluated a grid, straight printed strains, lengthy strains, and a bunch of different designs, and settled on a sample of quick strains.

As a result of this can be a reflective show, the extra gentle hitting the show, the brighter it’s. The analysis crew determined so as to add a entrance gentle to the show, one thing that was not a part of Triton, working arduous to make sure that the sunshine rays hit the ink layer at an angle that maximizes reflectivity. Utilizing a entrance gentle will increase power consumption, after all, nevertheless it’s price it on this case.

In consequence, E Ink’s new shade know-how, E Ink Kaleido, has considerably extra saturated colours and a greater distinction ratio than E Ink Triton. And at last, a full-color electronic-ink show was prepared to be used in shopper merchandise.

The primary official batch of Kaleido shows rolled off the manufacturing line in late 2019. We started transport to clients quickly after, and now you can see the know-how in merchandise just like the Hisense A5C, the iFlytek E book C1, and the PocketBook Colour, all of which had been launched in 2020. A second technology of Kaleido, known as Kaleido Plus, started transport in early 2021, with merchandise launched by Onyx and PocketBook and extra launching quickly. This replace improved shade saturation because of changes made within the printing sample and the sunshine guides for the entrance gentle.

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

Now we have a couple of issues to work on. Gentle effectivity, the fraction of incoming gentle that makes its approach again out to the person’s eyes, is sweet nevertheless it could possibly be higher. We’re persevering with to work on our movie layers to additional minimize this loss.

By persevering with to refine our printing sample, we’re additionally working to enhance decision through the use of denser circuitry within the electronics that sit under the ink layer and switch voltages on and off to maneuver the charged particles.

We’re additionally persevering with to work on our filterless, multipigment electronic-ink know-how. We anticipate to launch a brand new technology to be used in signage quickly, and it’ll embrace brighter colours and sooner web page updates. Sometime we would even have the ability to transfer this into shopper units.

When E Ink’s researchers set out exploring shade digital ink within the early 2000s, they thought it will be a matter of some years to fruition, given our experience with the know-how. In spite of everything, black-and-white e-paper took solely 10 years from idea to commercialization. The street to full shade turned out to be for much longer. However, similar to Dorothy within the Wizard of Oz, we lastly made it over the rainbow.

This text seems within the February 2022 print problem as “E Ink’s Technicolor Second.”




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