E Ink Talks About ePaper

Nov. 11, 2009
Technology editor Bill Wong talks with E Ink's Sriram Peruvemba, Vice President of Marketing, about ePaper

E Ink’s ePaper gives the Amazon Kindle its long battery life and great view. The Kindle is just one of many eBooks that take advantage of ePaper. Sony’s Reader Pocket Edition and Barnes and Noble’s Nook are other examples. Expect to see dozens of offerings at the 2010 Consumer Electronics Show.

I recently had a chat with Sriram Peruvemba, Vice President of Marketing for E Ink Corp., about E Ink and ePaper.

What is ePaper?

ePaper or Electronic Paper is a form of flat panel display that offers greater value than ordinary printed paper and conventional electronic displays. Ordinary printed paper is a very readable but not changeable whereas conventional electronic displays are changeable but not fun to read for long periods. Electronic Paper bridges that gap by being very readable (no eyestrain from backlights, paper like appearance) yet changeable. Like a book, electronic paper uses ambient light to reflect off the screen, the result is a great digital reading experience. It consumes significantly less power compared to typical laptop displays. You can read several thousand pages or for an entire week on an electronic paper based device before recharging the battery. ePaper based on electrophoretic display technology lends itself well to building flexible displays.

What advantages does ePaper have compared to other display technologies?

Biggest advantage is that ePaper mimics ordinary printed paper better than other display technologies. That means low eye strain while reading for long durations, the bistable nature of this display technology enables the use of a cell phone sized battery in a laptop sized display and that battery can drive the device for a whole week before requiring a recharge.

How does ePaper work?

There are many display technologies that are together called ePaper. The ePaper technology with the most traction is called Electrophoretic. E Ink Corp. and AUO both make different versions of electrophoretic displays. In case of E Ink’s Vizplex display, there are charged white and black pigment particles suspended in a fluid that is encased in a microcapsule. With the application of a voltage across the microcapsule and depending on the polarity, either the white or the black particles can be made to rise to the top of the microcapsule. An observer looking at the capsule from above will see a white or black dot. Several million of these microcapsules make up a ePaper display, combinations of white and black dots make for text and picture rendering.

What are the current performance characteristics of ePaper?

Reads like paper–has contrast of 7:1, higher than most ordinary newspapers. Next gen will have twice that contrast. The reflectivity of the displays is over 40%. The ePaper displays based on electrophoretic technology is closest in terms of producing flexible–shatter proof displays. Response time is roughly 250Msec which is much higher than LCD or OLED but is actually faster than what it would take for a human to turn the page of an ordinary book. True sunlight readable, very thin and light, a 6” eBook will run for a week or 7000 page turns on a single battery charge.

Is ePaper flexible?

The front plane of ePaper (E Ink Vizplex Imaging film) has been flexible from day one. Active matrix displays using this front plane rely on glass back planes which makes the module non flexing. Full flexible ePaper is expected in producting during end of this year. Several viable candidates demonstrated by dozens of companies using E Ink Vizplex. Please note that the above comments only apply to active matrix displays, the segmented (less information content) displays have been shipping in millions of units for a number of years and they are all flexible, their top and bottom planes are flexible. Examples of apps include wrist watches, smart cards, memory/battery indicators, shelf labels etc.

Do ePaper displays have to be rectangular?

Thanks for asking this question. No, they do not. We can make them any shape so far as segmented displays are concerned. (On a personal note, I have been promoting the concept of “think outside the rectangle” since most inquires we receive are for rectangular displays.)

How large can ePaper displays be?

We can tile them so there is no limit per se. On a single substrate, the largest demonstrated was 40” diagonal, by Samsung, using E Ink Vizplex material.

 What is the difference between segmented and grid ePaper displays?

 Segmented displays are direct drive, meaning each segment/giant pixel is directly connected to the driver whereas in case of active matrix, they are in a grid pattern and inter connected. One can drive them by energizing a particular row and column to isolate a given pixel.

What kind of drivers are needed?

In case of the Active Matrix displays, the drivers are similar to what is used in LCD, we use row and column drivers mounted on tab bonded flex attached to the TFT backplane. This in turn is driven by an ePaper controller (for example the Epson Broadsheet) and there are activities ongoing to bring this functionality into the application processor (a SOC solution). In case of the SURF display products (segmented display applications), we use controller-drivers, it is a direct drive method where each segment is directly addressed by the controller-driver. Once again, similar to segmented LCD products.

Can drivers be built into a microcontroller like LCD drivers? What kind of voltage, timing and connections are involved?

Yes they can be. We are working on System-On-Chip solutions where the drivers are being integrated into the microprocessor. Units will sample later this year. Typical voltage is 15V, lower voltages possible at the cost of response time.

Can developers get raw ePaper displays?We typically provide a kit which has display modules connected to drive electronics including sample software. Display modules can indeed be provided as well if the customer has the ability to drive them without the need for a kit.

What is the future direction of ePaper?ePaper displays have enjoyed tremendous success in the eBook application (over 40 models launched world wide) and moderate success in a whole host of other applications including wrist watches, smart cards, electronic shelf labels, signage etc. The eNewspaper application is emerging (larger displays, favors flexible display product) and is likely to be a significant market opportunity. I believe that the killer application will be eTextbooks for students. This trend has already started and with the arrival of flexible displays and color ePaper in 2010, that market is likely to ramp quickly. Flexible Active Matrix (because the segmented SURF displays are already flexible) and Color ePaper are the future trends.

When is color coming?We have demonstrated color ePaper and are scheduled to mass produce them by the end of next year. Here is what was said about our color ePaper:

“Then there was E-Ink Corp., which blew me away with a color e-book prototype, a flexible display no thicker than a laminated piece of paper and large-form e-ink displays that would make for low-power, high-contrast signage. Maybe I’m swayed by the newspaper industry’s need for technology like this, but if the future of e-books is as colorful and flexible as what I saw at SID, and if it gets here soon enough, the future might not be so grim for this industry after all.” By Omar Gallaga for NPR

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