History of E Ink Colour: E Ink Triton and Beyond

Even though E Ink technology has been present since the beginning of e-readers, achieving satisfactory colour displays has remained a challenge.

E Ink colour has recently become more common. However, E Ink colour has existed since the early days of e-readers. E Ink has tried various solutions to produce colour, and the development of Kaleido 3 represents another iteration. Since the beginning, E Ink has found getting colour to work challenging. According to E Ink’s technology officers, the challenge stemmed from the complexity of making colour work with their ‘waveforms’ algorithm that controls the mixture of black-and-white particles and how they appear at the top of the display.

Triton, announced in 2010, is E Ink's earliest attempt to introduce colour to the equation. It utilised a Colour Filter Array (CFA) that is still used with Kaleido 3. Triton was viewed as not ready, as the resolution was too low and the colours were not bright enough. The extra colour filter layer added an extra dimness that compromised the reflectance of external light—unlike LCD technology with a backlight, there was no way to brighten the display. At the time, front lights were not prevalent to counter the problem of dimness. Triton 2 attempted to resolve the dimness problem by introducing front-light compatibility. Yet, like Triton 1, it still suffered from the issue of low resolution and poor colour saturation. 

E Ink sought to develop Triton by improving the vividness of colour and resolution. The system adopted maintained the colour filter but brought it closer to the black-and-white layer. As noted, with Triton, the colour filter was printed on a separate glass layer. Kaleido - launched in Q2 2020 - does away with the glass-based layer and prints the CFA directly on the E Ink plastic film to get it as close as possible to the black-and-white display:       

We had created our earlier filters by printing semi-transparent red, green, and blue ink on glass. But this glass was an added layer. So we decided to print directly onto the plastic film that holds the top electrode, adding this step after our display modules were nearing the end of the assembly process. This arrangement would get the filters as close to the electronic ink as possible. It would also allow us to increase resolution, because aligning the filters with the display pixels could be done more precisely than was possible when using a separate surface.

E Ink Kaleido was developed in further iterations: Kaleido Plus and Kaleido 3. Kaleido Plus brought the CFA closer to the monochrome layer and introduced a new printing pattern to reduce light scattering and improve colour brightness and saturation. It also reduced graininess, ghosting, and flashing. Kaleido 3 (released in April 2022) further enhanced colour saturation by 30% and increased colour resolution from 100 PPI to 150 PPI.  E Ink also markets that Kaleido 3's front light supports 'Comfort Gaze', which is part of the technology trend of claiming to reduce blue light emission. 

E Ink Kaleido, utilising a CFA, should be considered a continuity and part of the Triton platform. Because it relies on a CFA, the problem of the screen's dimness is remedied either by very bright lighting conditions or by activating a front light by default. Added to the dim screen is a limited number of colours, poor colour saturation, and a noticeable reduction of contrast and crispness of black text. To put things in perspective, Triton produces 16 shades of grey and 4096 colours, like Kaleido 3. 

Will E Ink move beyond Kaleido's inherent limitations to another solution that does not rely on a colour filter and can generate a broader array of colours? There is hope in developing the multi-pigment ink system. In this system, a CFA is unnecessary; instead, colour is produced through coloured pigments in every pixel. In 2016, based on this multi-pigment platform, E Ink announced Advanced Colour ePaper (ACeP). E Ink Gallery is based on E Ink's Advanced Color ePaper platform and can produce 50000 colours (a significant upgrade on Kaleido’s 4096 colours) at a resolution of 300 PPI. 

By eliminating the CFA system, ACeP potentially offers the benefits of colour without the drawbacks of Triton and Kaleido. According to E Ink, Gallery 3 achieves a full-colour gamut through a four-particle ink system: 

E Ink Gallery 3 is based on the E Ink ACeP™ Advanced Color ePaper platform. In this platform, a full-color gamut is achieved through a four particle ink system: cyan, magenta, yellow and white, which allows a full color gamut at each pixel.

E Ink Gallery achieves a full-colour gamut, including all eight primary colours, using only four coloured particles (source: E Ink).

E Ink Gallery 3 improves refresh rates compared to previous iterations. Yet it is far slower than Kaleido and is still impractical for consumer devices like e-readers and e-notes. As a result, ACeP solutions like Gallery 3 are primarily restricted to signage, public information boards and picture galleries.