The E Ink display is great in that it comes across as a digital incarnation of print on paper. That way, it has several qualities of the latter, which include having the same feel like real paper. That also means the least strain to the eyes even after reading off the E Ink display for an extended period. Besides, it is almost as readable under direct sunlight as off of it, this when most other electronic displays get washed out in bright conditions.
While all of that is nice, E Ink still suffers from an inherent disadvantage, if it can be so said. The displays are restricted to just black and white and the intervening shades between them. Those do not come in the way of reading most e-books though the splash of color is missed when reading some content such as comics, manga, some PDF, or other stuff like academic materials that come with colored illustrations.
Unfortunately, it is here that the otherwise almost magical E Ink displays have come to falter. Take for instance the E Ink Triton that was launched in early 2000. It involved the placement of a color filter, essentially an array of red, green, and blue colored squares that are printed on top of a glass layer placed on the standard E Ink layer. The basic functioning is that when the white pigment would move to the top in response to the electric charge applied, the light would reach the human eye from within the RGB filter.
It was a nice attempt and relied on the fact that most colors that we humans get to see can be created with red, green, and blue colors. That also explains the use of RGB emitters or filters with LCD or OLED displays though that didn’t seem to work with the e-paper tech as the colors thus produced ended up being dull while the resolution too was simply too low.
This again can be attributed to one of the inherent positives of the e-paper display, that of its reflective property. What that means is it depend on external light and unlike LCDs or OLEDs, does not have a light source of its own. External light that is incident on the E Ink layer gets reflected back to the human eye to create an image, which is similar to the way we see the objects around us.
However, having more layers between the E Ink layer and the human eye leads to scattering of light in between, leading to a dimming effect so that the display eventually seems to be of low resolution. According to E Ink, the resolution of the E Ink display would drop by one-third by the addition of a color filter array. That might be acceptable for larger displays used as digital signage that need to be viewed from a distance but the loss of resolution would become glaring for a hand-held device.
Next came the Multipigment e-paper also known as the E Ink Spectra which can be considered quite successful in its area of operation, that of electronic shelf labels. It also is basically the same as the monochrome E Ink panels though the difference here is that there are three pigments – black, white, and red or black, white, and yellow – at work to create the colored effect. However, the particles this time are of different sizes which E Ink said makes them better sorted as larger particles will tend to move slowly in liquid than smaller particles.
Apart from introducing varied sized particles, the electronics too were modified to allow for the passage of varying amounts of charge, which can be anything in between from a positive to a negative charge. Yet another change introduced was that the container shape was no longer a perfect sphere. Instead, the particles are held in a trapezoid-sized container named Microcups which the company said allows for better control over the vertical position of the particles. Typically, the particle closest to the surface will lead to that color having a greater intensity among the others.
Also, unlike the monochrome E Ink panels, the waveforms were adjusted to push and pull the different particles to different states as was required for the formation of a particular image. E Ink added the fourth particle – red – to the system as recently as 2021 which made the ESLs all the more stunning. While the four colors can’t be combined to create full-color images, it still impresses with its deep contrast and the highly saturated colors and is just right for ESLs.
It is the Advanced Color ePaper (ACeP) that came in next and made for a significant improvement over its predecessors. Interestingly, here too, there are four colors at work though the black has been removed. Instead, it is cyan, magenta, and yellow that work along with the white – the paper – to create the colored effect. Or more specifically, the colors are made to stop at different levels using varying amounts of charge to create up to 50,000 colors which is typically what we have in newspapers or in watercolor art.
However, while ACeP has been great, it still missed out on the wow factor. That led the technical team to get back to the drawing boards and this time, they went all the back to the Triton displays all over again. However, while previously the semi-transparent red, green, and blue ink were printed on glass, the team decided to print it on the plastic film itself to let go of the glass layer. This would lead to increased brightness and contrast, at least theoretically.
Also, instead of a square grid for the filters, a combination of short lines was chosen after evaluating different options. Among the other changes introduced was the addition of front light though that was done in a manner the light rays incident on the E Ink layer causes the maximum reflection. This led to the development of what has come to be known as the E Ink Kaleido color display having remarkably better color depth and a higher contrast ratio compared to the E Ink Triton display.
While Kaleido came into being around 2019, the company managed to come up with an even improved version of the same in the form of the Kaleido Plus in 2021. The latter which made it to devices such as the Onyx Boox Nova 3 Color and Pocketbook InkPad Color had even better color saturation and is achieved by optimizing the filter pattern as well as the light guides from the front light.
E Ink however has stated they are still working to improve the color display all the more to achieve even higher resolution color displays in the future.
With a keen interest in tech, I make it a point to keep myself updated on the latest developments in technology and gadgets. That includes smartphones or tablet devices but stretches to even AI and self-driven automobiles, the latter being my latest fad. Besides writing, I like watching videos, reading, listening to music, or experimenting with different recipes. The motion picture is another aspect that interests me a lot, and I'll likely make a film sometime in the future.
